To review the holiday entitlement calculation when you get unexpected values, you can check the historical changes to entitlement. To do so:
Click Access Button
then click Employee.
Click the relevant employee and then click the Planner tab.
Click Settings then, next to the This Year field, click the clock icon.
TOIL and carryover are included in the this year total, which may explain the unexpected values. You can verify this in the history for the this year field and within the TOIL and carryover histories in the planner settings.