Yeah your math is way off.

We already knew/know the starting point of 61 and 65 and their applicable ranges and private keys.

61 is in the 61 bit range.
A 1 followed by 15 zeros thru a 1 followed by 15 f’s
65 is in the 65 bit range.
A 1 followed by 16 zeros thru a 1 followed by 16 f’s.