'Base count' is the total number of combos. 'Optimized count' is the number of combos after accounting for any card removal.
What's happening is you probably have a few hands in the simulator with cards that are removing combos from the optimized count of AsK8Q:xx. Any specific card will do that (such as As) whereas more general ones won't.
AsK8Q:ss is any AKQ8 combo with the As and at least one other spade. (Up to four spades in the hand. To restrict it to only two, you have to exclude three-spade combos with '!sss'.)
AxK8Q:xx is any AKQ8 combo with at least two cards of one suit, because it's apparently treated by PPT as identical to AK8Q:xx. For example, AhKcQc8s is included.
For any suited ace you'd want to use AK8Q:Axx, for which you'll get the expected 148 combos.