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I could see the metronome telling what measure number it was on, but not the total number of measures (unless the user input that information).

True, but the user would need to keep track of which measure they were on in comparison it to what the metronome said it was on. If you had a lot of measures, complex measures, large intervals between measures for some instruments or repeats that may pretty difficult to do. Numbering every measure on the score in a readable manner may help before uploading to MS.