Dispater is not, entering into this attention, particularly expecting that Carissa Sevar will be worth 30 Wishes to Him, though He does hold out some probability of it. The vast majority of all mortals who ever were or will ever be, cannot be the most important key to Hell's conquest of Pharasma's Creation, or even have a 1% chance of being that; the prior odds are against it - but only exponentially rather than superexponentially so, it is the kind of incredulity that evidence could overcome, and few mortals already receive this much divine attention.
And what He can see, even with half His full attention on this one mortal, is still far less than any fragment of Nethys sees at a glance. He is looking at Carissa Sevar's thoughts as they form, not reading out her whole memory and analyzing it; He's a god, not a superintelligence.
But neither is He only as clever as INT 33 / WIS 30 might have you believe, for His intellect is not only clever but large. He integrates many other facts than those visible in only this moment to His eyes, rumors traded about Dis that have passed up to one fragment of His attention or another, rumors passed up out of spies in the mortal realm; He fires off inquiry-demands to several Counts of Hell about why exactly they traded or made offers at the prices that they did -
Probability is twisted about this one, not in any way directly visible to any sense He has, but implicit in a hundred facts around her. It is not His first time or His hundredth in dealing with a hero out of prophecy.
Probability is twisted about this one, and that is not something that should have been possible in Golarion, that has been Rovagug's vault through ages and around which prophecy has now entirely shattered.