Update src/kriscv/kdist/riscv-semantics/lemmas/int-simplifications.md

Author: Stevengre

src/kriscv/kdist/riscv-semantics/lemmas/int-simplifications.md

@@ -36,7 +36,7 @@ module INT-SIMPLIFICATIONS [symbolic]
   rule [bytes2int-and-255-noop]: Bytes2Int(X, LE, Unsigned) &Int 255 => Bytes2Int(X, LE, Unsigned)
     requires lengthBytes(X) <=Int 1 [simplification]
   rule [bytes2int-zero-prefix-or-to-concat]: Bytes2Int(b"\x00" +Bytes X, LE, Unsigned) |Int Y => Bytes2Int(Int2Bytes(Y, LE, Unsigned) +Bytes X, LE, Unsigned)
-    requires Y <Int 256 [simplification, concrete(Y)]
+    requires 0 <=Int Y andBool Y <Int 256 [simplification, concrete(Y)]
 ```
 
 ## Equality Lemmas