Accept that each Chicken Drop session is random
A 7x7 grid gives no way to know when the bonus round comes. Whether 4, 5 or 6 BONUS chests land in a session is not known before the first spin, and the frequency is not known either. The result of one session is random, whatever RTP version runs.
Two RTP versions exist for Chicken Drop, and the game rules show which one runs on this site. The rules panel in the game is where to check it before the first spin. Each version has its own RTP, so the same bet can return a different share over time.
A top win of x5,000 the bet is the ceiling of Chicken Drop, and it is reached very rarely. No session can be planned toward it, because the outcome of each spin is random. Read it as a limit on the top prize, not as a target for any play.