Add clarification on the comparator

Author: rahulketch

parquet-column/src/main/java/org/apache/parquet/schema/PrimitiveComparator.java

@@ -208,6 +208,9 @@ public String toString() {
 
   /*
    * This comparator is for comparing two timestamps represented as int96 binary.
+   * It is a two level comparison.
+   * Days (last 4 bytes compared as unsigned Little endian int32),
+   * Nanoseconds (first 8 bytes compared as unsigned little endian int64)
    */
   static final PrimitiveComparator<Binary> BINARY_AS_INT96_TIMESTAMP_COMPARATOR = new BinaryComparator() {
     @Override