Minor docs update to sdk.Int (#9126)

Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>

types/int.go

@@ -69,9 +69,9 @@ func unmarshalText(i *big.Int, text string) error {
 
 var _ CustomProtobufType = (*Int)(nil)
 
-// Int wraps integer with 256 bit range bound
+// Int wraps big.Int with a 256 bit range bound
 // Checks overflow, underflow and division by zero
-// Exists in range from -(2^maxBitLen-1) to 2^maxBitLen-1
+// Exists in range from -(2^255 - 1) to 2^255 - 1
 type Int struct {
 	i *big.Int
 }