How can I format to time column in Numbers?

That helps a little, but still doesn't quite answer the question.

What value was entered in the ToD column?

If you entered, say, '1215' then Numbers will interpret that as a Number value, not a date or time, since it doesn't conform to any standard date/time format.

If you entered '12:15' (including the colon), then it should recognize this as a time value.

Not enough info in your post to tell.

You're showing the Cell Inspector, which should format a cell as a Time string, but we're not seeing the cell(s) in question to know what you're seeing, or what you expect to see.

Note that if you have the cell format set to Date & Time and you enter a value that isn't valid (e.g. 123) then the cell format will revert to Automatic, so the cell formatting only works as long as Numbers can interpret the data as a date. Maybe that's the problem?

What value is in the cell you're trying to format?

Ahh, coming from Excel, yes, the rules are a little different.

I do think Excel is a little 'smarter' when it comes to determining cell formats, but even then I can't find a setup in Excel that automatically interprets '1215' as time '12:15'.

Even for a 'Time' formatted cell, entering '1215' results in a date of '4/29/1903 00:00:00', which is 1215 days off Excel's epoch time of 1/1/1900, so it appears to interpret raw numbers as day offsets, not HH:MM.