I recently upgraded the electerical service to my house. The contractor installed dual, 30 amp breakers for 220v service. He used, what appears to be, four 10AWG wires run from the main breaker panel to a junction box out in the garage about 32 ft away. I plan to add an additional 35 ft of wire to my proposed spa location.
I'm worried that the 10 AWG wire is not sufficient?
Please advise. Thanks a lot!!

10 wire is only good for 30 amps. It will depend on the amps of the spa.
Do the wire go into a sub panel and can they be updraded?

Thanks for the reply.
The wire goes into a GFI breaker box mounted 30 ft away from the main breakers.
Thanks again!