I work in the public sector. I took two weeks of long service leave but they’ve deducted 14 days, not 10. Is that correct?

Long service leave (LSL) is different from annual leave as it is an entitlement based on your overall service and the actual period of absence taken is based on calendar days (inclusive of non-workdays) not actual current hours. It is also standing practice that one week of long service leave equates to seven days of leave, and long service leave is generally taken in week blocks, so yes, if you have opted to take your LSL at single pay, that is correct that your balance was deducted as seven days for one week of leave.