FFT members already had their sale.........what's available tonight is whatever has not sold so far to FFT members.
It will be VERY tough to get Cat1 seats in any of the main 3 stadiums - most all those seats are taken by FFT Pre-Sale or blocked for the mult-day package deals - getting General Admission also not an issue on the first day of the sale.
Depending on how many tickets you need will also be a factor - 1 category 1 seat in Lenglen or Centre Court possible - getting 3 or 4 together very tough. Best be prepared to settle on GA or Cat 3.
If you do not get what you want wait a bit and use the FFT VIAGOGO system in a few weeks - almost always able to get decent seats.