When I last tried to check the total amount of creatures in Amethyst it did not work correctly. For TUM specifically, Maiko should include a variable like
!?FU(GetMaxMonsterId);
!#VA(result:x);
!!VR(result):S291;

so we can get amount by calling !!FU(GetMaxMonsterId):P?(lastMonsterId:y);

@Archer and Daemon, about the EA bug, Bersy told me he is aware of it but currently also very busy, so we just need patience