pro rata calculations

We have noticed when processing new starts / leavers if they start on 1st of month (being a weekend) and due to be paid the full month, Staffology does not pay a full month. The same if a leaver 31st December, Staffology is paying more than full monthly basic. Is there anyway we can set up Staffology to correctly process new start / leaver pro-rata or do we need to change “pro-rata” rule to manual for each employee that is being calculated wrong to override this? why is there not a flag in pro-rata settings or working pattern rule to say if someone working full month then it should not exceed period salary or if they start on 1st of Month, even if on a weekend, should be full month regardless if weekend. Can you confirm further how we can proceed?