5 days for Ai is by no mean short! If it can solve it, it would need perhaps 1-2 hours. If it can not, 5 days continuous running would produce gibberish only. We can safely assume that such private models will run inferences entirely on dedicated hardware, sharing with nobody. So if they could not solve the problems, it's not due to any artificial constraint or lack of resources, far from it.
The 5 days window, however, is a sweat spot because it likely prevents cheating by hiring a math PhD and feed the AI with hints and ideas.