Adding and averaging across multiple columns.

Simple - and totally doable in Numbers.

Your problem is the format of the Time fields. You have them set as Date fields. So, while you see 03:29, Numbers, internally, knows this as something like "January 1st 2025, 3:29am" (i.e. a full date/time value) and you're just opting to show the time component.

Given this, how would you expect Numbers to 'add' January 1st, 2025 3:29am to January 13th 2025, 10:20am? It can't be done.

For this, the cells need to be formatted as Duration values, not Date:

As duration fields, they have an intrinsic numerical value that can be summed, averaged, etc.

Also, to avoid confusion, it's best to enter the cell value as something like "3h29m' rather than 3:29 since it eliminates any ambiguity over days/hours/minutes/seconds, etc. The formatting can display as 3:29, it is only the data entry that matters.

Hope that helps.

As an aside, it's your spreadsheet, but you could save yourself a lot of hassle by formatting this differently. The gaps between the days, and the days spread across two columns makes this much harder to manage. I'm guessing you have your reasons, but it may be worth considering a different layout.

Ahh, the joys of working for the 'powers that be' :)

Even so, if this is taking a long time to manage there may be opportunities to reduce your overhead.

I'm thinking that it may be possible to have one 'master' sheet for all days/hours worked, and you enter your data on this. Then you have a series of supplemental sheets that 'pull' data from the master sheet and format it in the way the report demands. You're still entering the data, but at least it would be a more consisent manner and it would reduce the burden of having to work in these fractured tables.

That said, once the master setup is done it's mainly a maintenance task to update the hours, so the gain may not be that great from a time management perspective... maybe more of a personal edification thing :)