The Cube is a high-yielding supercomputer that generates ~3,000 ke/s in processing power. Depending on upload bandwidth and network difficulty this will generate ~150-500 PKT per day, paid every minute. Mining yields will vary based on mining competition, which is why there is such a wide range of yields. The more miners, the fewer rewards are shared amongst all miners.
Every 100 days there is also a decimation that occurs on the PKT blockchain, which reduces mining rewards by 10%. The best time to accumulate PKT is now.