The 'bt' stands for BridgeTrak, which is the name of the software used to submit and answer Biotics 4 support questions. The number refers to the issue number. When you run any SQL update statement in Biotics, you have to include something in the rec_last_mod_user field because of a database trigger that requires a value. So, when we send out patches to the network, we typically put the BT issue number in rec_last_mod_user in the script that gets run to solve whatever problem was reported in that issue. The next time a table that was updated by the script is updated by a user, the 'btxxxx' will be replaced.