Mac Time Machine manual not auto backups query?

[slope]

New iMac successfully accepted my data transfer from old Mac Mini. Which had an external WD 1TB back up drive - and for some reason I now forget, the WD was partitioned.

So after the hunky dory migration to the all new machine, I decided to erase the WD external drive and un-partition it so as use it solely as a back up drive for the new iMac.

New iMac backs up fab and groovy onto re-formatted WD external drive - approx 300GB in all.

Again through Time Machine, I've performed manual incremental back ups onto the WD*

Today I did the same but noticed it was a 200GB transfer, not the usual one weeks worth of not much apart from some new RAW camera files. The 1TB WD is now over half full.

Why?

Could it be that since the previous manual TM back up, I successfully changed the name (that was annoying me) of the 'home' folder in "USERS"

Please excuse me for being a bit of a total amateur 'mucker with computing stuff' - maybe I like the danger? Certainly deleting previously named home folder had a certain frisson

*Can't get my head around why TM back ups need to happen every hour or whatever the 'auto' regime defaults to. Once a week seems cool enough for me?

[Jim400]

I’m not sure, but I suspect it’s because you renamed the folder, Time Machine will probably have taken a new copy of the field and folders contained within and be storing them in addition to the contents of the old folder (as it were).

Was there ‘about 200 Gb’ of data in the users folder? (Even though it’s he same data and nothing has changed)

Don’t worry about it, the Time Machine folder on the external drive will slowly increase in size until it fills the entire HDD, then it will start overwriting old change, such as the old users folder that doesn’t exist any more. (Which was probably the reason you partitioned the drive originally, to limit the maximum backup size. I did exactly the same thing on a previous TM backup dive).

[slope]

Was there ‘about 200 Gb’ of data in the users folder? (Even though it’s he same data and nothing has changed)

I didn't check the size of the previously named home folder - but the newly named one is ~200GB - ergo . . . 

Just remembered - the migration from the old Mac was interupted and I started again from the TM back up, which also was stopped (can't recall why now) part way though. The third attempt was successful. So I ended up with 3 users and finally 1 home folder - what the Mac did was automatically rename each User by suffixing the second and third, 'username' 1 2 and 'username' 1 2 3. The latter became the home folder. So it all looked 'messy'

But happily all sorted now