u/Electrical-Gain4290

If someone has a permanent part time contract for 15 hours a fortnight but generally works 24 to 30 hours a fortnight and they apply for annual leave, do they need to take the full 24 hours (or whatever hours they worked in the most recent fortnights) or can they apply to take the fortnight off work and only apply for 15 hours annual leave? (Uni student needing to take time off for exams so their preference would be to only need to apply for 15 hours otherwise they are using up all their leave for exams and won't be able to take any holiday time as such) Thanks