this interval has been checked
Ok. Then You should write checked not check.
What is the full range for 62 bit key?
Hex: 0x2000000000000000 - 0x3FFFFFFFFFFFFFFF
Dec: 2305843009213693952 - 4611686018427387903
If you do an analisys you will see that all found keys are over 50% of it's range (
see here), hence I would say that you can skip the first half and search between 51%-99%.