Please note that when multi-merging it is one transaction so if for instance you are merging 6 or 9 farms at a time, you have one 36% chance of the minor bonus. If you win the bonus, you will receive that same bonus for all merges. If you prefer 1 chance of bonus per a merge, please use single merges at a time. Over time with lots of merging, say of farms, the chance of a bonus is mostly the same. But users doing rarer merges, like towns or cities may prefer single merging due to the bonus chances being per merge. The benefit of multi-merging over single merging is reduced CPU (almost 70% reduction) and less time.