I assume you mean whether you'll be booked into an instant-upgrade fare class if you choose the Main fare? You can infer it by choosing the MVP/Gold/75k/100k radio buttons (on the left) and then looking at the Premium Class Upgrade and First Class Upgrade columns. If the Main fare is greater than or equal to one of those, then you know that if you book the Main fare, you'll get an instant upgrade to either PC or F at that status level. So for example, if you select "MVP Gold" and then you see that the Main fare is the same as the "First Class Upgrade" fare, you know that Main must be booking into the K fare class or greater. So if you select the Main fare *and* U space is available, you'll get an instant upgrade to F if you're MVP Gold or higher.

Still a bit cumbersome to have to select the radio buttons (and possibly several of them to narrow it down), but faster than having to add it to your cart in order to see the fare class.