It actually seems likely.
Mueller's report starts the events that led up to the actual 'happening'
It all depends on what the countdown is 'for' however - is the countdown for the beginning of the happening - or the countdown 'to' the start of events that lead to the happening.
Given the amount of time left and wht all has to happen before the happening however, I must concede, it does seem more likely that the countdown is referring to Mueller's report being turned over.