Bench Power Supply Current Rating

The supply can deliver up to 5 amps at up to 30 volts.

The voltage and current ratings are both maximums, and are independent of each other - you can't expect to get 10 amps at 15 volts.

Depends on the power supply, but generally a bench power supply is rated at max everything, so that would be 5 A at 30 VDC, aka 150 W.