Currently endpoints return count which is intended to represent the total number of records matching the query. Due to some API inconsistencies a few endpoints instead return a count which represents the number of remaining records (accounting for your current pagination position). Apparently this inconsistency will be sorted out so that count always represents the total records. I propose that at the same time a new "remaining" count be returned as part of the results as well. This is because if you've got a large number of records that you're needing to process it's actually quite nice to be given not only the total number of records but also the number that are remaining for you to process. This helps you keep track of progress without having to rely on your own count of how many you've done so far which isn't always practical if you're going through the full number in multiple different chunks at different times.

So if you were using the Constituent List and your query returned 100,000 records total and you'd just retrieved results 70,000-70,500 of them you'd get count=100,000 and remaining=29,500 (assuming that remaining only includes those after the current page)

See also https://community.blackbaud.com/forums/viewtopic/426/33465