We ask what the audience looks like before asking how many there are. Each stage writes down what it changed and why. Columns without a written meaning are left out rather than shipped undocumented.
Date normalisation
Putting every date in one format and one timezone before any comparison runs.
Format handover
Delivery in the structure your systems already accept, tested on a sample so nothing needs reworking afterwards.
Hand-off
Delivered in the format your systems take, with the field definitions written down.
Ask for a count and you will get the number and the definition behind it.