But it's still probably just an estimate.
My understanding is that it may overshoot or undershoot between blocks (because it doesn't know the exact number, only the average) but the average over all these years should be very close to the real number.
And what percent is that number, from all the possible 2^256 SHA256 hashes?
2^70 / 2^256 = 2^-186 = 1.02 x 10^-56 =
1.02 * 10^-54 %0.00000000000000000000000000000000000000000000000000000102 %Very small. Exponents are powerful.
Edit: fixed # of 0's
And just wondering, what happens when it reaches 100% or 2^256. And yes I agree, exponents are amazingly powerful:)