diff --git a/finetune/util/table_labeler.py b/finetune/util/table_labeler.py
index 06bf434e..0c8f776f 100644
--- a/finetune/util/table_labeler.py
+++ b/finetune/util/table_labeler.py
@@ -1,6 +1,7 @@
 """
 Finetune-style interface for running a pipeline of table and non-table models.
 """
+import bisect
 import copy
 import functools
 import logging
@@ -438,8 +439,12 @@ def __init__(
 
     def get_axis_spans(self, context, token_bounds, context_key):
         max_row = max(r[context_key] for r in context)
-        row_spans = [
-            [
+        row_spans = [[] for _ in range(max_row + 1)]
+        for c in context:
+            row_idx = c[context_key]
+            if row_idx < 0:
+                continue
+            row_spans[row_idx].append(
                 {
                     "start": c["start"],
                     "end": c["end"],
@@ -448,11 +453,7 @@ def get_axis_spans(self, context, token_bounds, context_key):
                     )
                     + 1,
                 }
-                for c in context
-                if i == c[context_key]
-            ]
-            for i in range(max_row + 1)
-        ]
+            )
         return self.combine_row_spans(row_spans, token_bounds)
 
     def chunk(self, table_text_chunks_and_context):
@@ -594,10 +595,13 @@ def _make_chunks(self, row_spans):
                 break
         max_len_chunks = []
         temp_rows = []
+        temp_row_tokens = 0
         context_included = False
         for row in row_spans[n_rows_context:]:
-            if self._num_tokens(context + temp_rows + [row]) < self.max_length:
+            row_tokens = row["num_effective_tokens"]
+            if (context_tokens + temp_row_tokens + row_tokens) < self.max_length:
                 temp_rows.append(row)
+                temp_row_tokens += row_tokens
             elif len(temp_rows) == 0:
                 # The current row is too long to use any context at all.
                 max_len_chunks.append([row])
@@ -605,6 +609,7 @@ def _make_chunks(self, row_spans):
                 context_included = True
                 max_len_chunks.append(copy.deepcopy(context) + temp_rows)
                 temp_rows = [row]
+                temp_row_tokens = row_tokens
         if temp_rows or not context_included:
             max_len_chunks.append(copy.deepcopy(context) + temp_rows)
         output_spans = []
@@ -626,11 +631,18 @@ def _make_chunks(self, row_spans):
         return output_spans
 
     def combine_row_spans(self, row_spans, token_spans):
-        def mark_token(t):
-            t["used"] = True
-            return t
-
-        total_num_tokens = 0
+        token_starts = []
+        token_ends = []
+        token_spans_monotonic = True
+        for token in token_spans:
+            token_start = token["start"]
+            token_end = token["end"]
+            if token_starts and (
+                token_start < token_starts[-1] or token_end < token_ends[-1]
+            ):
+                token_spans_monotonic = False
+            token_starts.append(token_start)
+            token_ends.append(token_end)
         combined_rows = []
         for row in row_spans:
             row_out = []
@@ -640,14 +652,28 @@ def mark_token(t):
                 else:
                     row_out.append(span)
             for row_span in row_out:
-                row_span["num_tokens"] = len(
-                    [mark_token(t) for t in token_spans if overlaps_token(row_span, t)]
-                )
+                num_tokens = 0
+                if token_spans_monotonic:
+                    token_idx = bisect.bisect_left(token_ends, row_span["start"])
+                    while (
+                        token_idx < len(token_spans)
+                        and token_starts[token_idx] <= row_span["end"]
+                    ):
+                        token = token_spans[token_idx]
+                        if overlaps_token(row_span, token):
+                            token["used"] = True
+                            num_tokens += 1
+                        token_idx += 1
+                else:
+                    for token in token_spans:
+                        if overlaps_token(row_span, token):
+                            token["used"] = True
+                            num_tokens += 1
+                row_span["num_tokens"] = num_tokens
                 # Accounts for the fact that cells are duplicated when they span cells.
                 row_span["num_effective_tokens"] = (
                     row_span["num_tokens"] * row_span["max_cell_span"]
                 )
-                total_num_tokens += row_span["num_tokens"]
             combined_rows.append(
                 {
                     "num_tokens": sum(r["num_tokens"] for r in row_out),