I suspect it's for 223 Remington, 0.224 bullet and that amount of Varget fits with the 223. Hornady's data is in general a bit on the conservative side but I have also found my most ACCURATE loads using Hornady's data. You have a choice here, to you want maximum accuracy or do you want maximum velocity, in my experience it is rare for the two to coincide. If you want maximum Velocity I would suggest you look at Hodgdon's data, in general Hodgdon's data runs a bit "hotter" that Hornady.

However do keep in mind with a 75 grain bullet in 223 you won't see velocities in the 3200 fps range, the case just doesn't have enough capacity. I'll also note that higher velocities will increase the wear rate on the barrel.

Being a cheapskate and someone who prefers Accuracy over Velocity I load using Hornady's data. Means I use less powder per round and my barrels will last longer. As for Accuracy I have one load for my precision rifle in 223 Wylde that puts a 68 grain Hornady BTHP into 3 shot groups under 3/10 inch at 100 yards and 5 shot groups are under 4/10 inch.