SQLOptimizerForOracle_9.3.3 Version question

We just downloaded the 16.1.53.1594 version of Toad for Oracle

We noticed that the version of the SQLOptimizerForOracle is 9.3.3.1526.
But the current version of SQL Opt that we have with Toad 15.1 is 9.3.4.1759.

It is only a minor x.x.1 point difference but we were wondering why the the version number seems to have reverted? Presumably a bug issue?

We are proceeding with the installation as is but were curious if it is correct.

Thanks,
Alan