Does anyone know how often DL normally updates fare class inventory as reflected on delta.dumb and as displayed on EF?

I'm watching a flight today, for travel about ten days from now, and I'm seeing inventory of F9 P9 A7 G6 but only 4 FC seats open on the seat map, which had 10 FC seats available out of 16 yesterday in the early evening. In fact, until today DL was only selling P and F fares for FC, but now G and A fares have appeared (but they're not cheaper, apparently due to advanced purchase requirements). It's a route where the sale of six FC tickets would seem surprising and the FCM offers I've received aren't very tempting either.