But... When i try to reverse the last (let's say) month: I'd have to go back to (x-4464) => 6 blocks/hour * 24 hours/day * 31 days/month.
By the time i reached height (x), the rest of the network would have reached height ~(x+4374). Oops
I don't understand how the 4374 was obtained.
Let's say I have 51% of the hashrate and 49% of the hashrate is owned by honest miners.
I mine 4464 blocks during a month. Number of blocks mined by honest miners can be easily calculated using proportion method.
So, number of those blocks be
4464*(49/51) = 4288.
Am I missing something?