It took it figuratively too, but as an indication that 57 is the last level at which a channeler can lift anything with air, so Morgase is likely 57 or 56, as ten levels down that cut-off mark seems way to far below, figurative or not.

I'd have to check the full context, but I remember that Terez too was under the impression he had Morgase in mind when he wrote that note, which iRRC is in a file dating from between COT and KOD where the Morgase episode takes place. Sorilea isn't far from there too. IMO, it's intentional that those two are quite similarly weak, but a lot of people misunderstood where he was going with that and tought Sorilea "much stronger" because unlike Morgase her teachers persisted as long as necessary to train her as much as she could learn, and more. The WO (in a scene scorning the AS training) told us that in the books... Sorilea was an example of the results, especially in the scene with Cadsuane and the weave for Travelling..

I think it was meant as an illustration of how the WT, short of effectives, wastes the potential of women like Morgase, by showing that Sorilea was trained nonetheless and could teach channeling to pupils, even without using an angreal and in her days, even without linking. The WT is all the more unforgivable given the fact that they have angreal gathering dust rather than being used (and besides, a very weak woman like Morgase can link with her pupils to demonstrate weaves if necessary...). It was a flaw in the WT worldview, those "cut off" levels at which they rejected people that they could have found a use for.