Clock has been verified as many times as POTUS has verified Q, probably more.
It's not useful as a prediction tool. If it were useful as a prediction tool it could be used against Q.
Instead, use it as a means of verifying things. It is extremely effective at demonstrated foreknowledge. The "mathematically impossible" drop is relevant in this regard. If things were to be 100% at random, the degree of synchronicity the Qlock demonstrates would be mathematically impossible. So the Qlock must be part of the plan.