To Carissa M:
The manual update instruction you directed me to says that it is for Windows and specifically says that it is not available for Mac.
The size of the auto update is the same as I encountered in the 2020 TT program ... I don't think that's a coincidence. The one time I got TT 2021 to open, after passing "install and relaunch", the message was that there are no current updates.
