Hi Chezz22
Sorry to see that no one has offered their assistance with your query.
From what I can see from the screenshots provided, the payslip does appear to have been entered correctly to accrue the alternative holiday date (i.e. it is a negative). However, it is likely that a previous value was listed on the employee's record with an alternative holiday, therefore, it has shown as a negative (generally this value would be a positive 1 day based on the pay recorded).
To remedy this my recommendation would be to manually work out what the Alternative holiday value should be for the employee i.e count the number of public holidays worked less alternatively holidays taken. This gives you a result of what the alternative holidays should be. You can then manually add that to the employee's record -- Maintenance>>Maintain Employees>>Leave Details>>Other Leave>>Alternative Holidays -- Current Alternative Holidays Due.