Discrepancy in the number of results returned from Piwik APIs for the same range of a period

Hello team,

we found there is a significant discrepancy in the results returned from Piwik API for the same period of time.The Issue was noticed when i split the range of time from 08/10/2020 to 31/07/2021 into small batches of periods/queries it returns ~75K result, however If i run the call for the the same period in one batch/query it returns a different number of results (~21k)

I noticed same behaviour from UI also. (Behaviour → Page) . please let me know if this is a known issue or anything is missing here?

we are using piwik 3.6.1