private static int generateEventOffset(TXState txState) {
    long seqId = EventID.reserveSequenceId();
    return (int) (seqId - txState.getBaseSequenceId());
  }
Calculate and return the event offset based on the sequence id on TXState.

@since GemFire 5.7
geode-core/src/main/java/org/apache/geode/internal/cache/TXEntryState.java