You are legally entitled to a minimum of the equivalent to 5.6 weeks (28 Days) of holiday, including Bank Holidays, per year in the UK. For jobs like ours at Tesco that requires some conversion to hours, and if you are hear on a three month contract then if you go over a quarter of the annual allowance then they'll take it out of your last paycheck (conversely if you leave before the end of the holiday year on the 31st of March they will have to pay you for the unused hours).

15 * 5.6 / 4 = 21 Hours (or 1.4 weeks) of holiday in your first three months of work.

The Acquired Holidays on the payslip are the amount you've earned now, and that if you left immediately they would have to pay you the cash equivalent of.

There are details about Tesco's leave policy on Colleague Help here: https://colleague-help.ourtesco.com/hc/en-us/articles/360001313703-What-s-my-holiday-entitlement-for-colleagues-on-the-Work-Pay-Payroll-System-