Sometimes it could also be the fact that you have changed some setting in the system which would have caused the remaining allowance for an employee to change from its original figure.
For example if you have set the checkbox for "Main Holiday allowance inclusive of Public Holidays" as "Yes" in the system then this would deduct the Public Holidays from your allowance and it can further effect the remaining allowance for the employee.
You can find that setting under "https://app.leavewizard.com/SystemAdmin/Setup/Settings.aspx". Below is the snapshot for that:
If this setting is set to "Yes" then you would see an extra column of "Included Public Holidays"
in your allowances page configuration. Below is the snapshot for it: