You have to do 3 (I think) antigen tests so its possible some are the same case with 2 positive tests.Does that mean that 1500 ish got a positive on an antigen test and never went for a pcr or naybe that many were false positives on the antigen or a bit of both.
The swabs numbers are always slightly higher than cases for that reason. Sometimes people have 2 tests but its just one case of covid.