Detached Garage Wiring


We just purchased a home with a detached garage. The feed for the garage comes from a single pole 30 amp breaker 10-2 wire which is fed into a disconnect in the garage. A jumper wire 10 gauge is then used between the two poles of the garage disconnect. There is then two 20 amp breakers in the garage disconnect with 12-2 feeding lighting and outlets. Is this safe? It seems it would have made more sense to run 10-3 from a 2-pole 30 amp breaker, but I don’t want to re-run the wire if I don’t have to considering its buried.