The way they calculate an expected normal time is quite clever. They let a few of the most consistent horses set it. Cool thing is the horse can totally suck as long as it totally sucks in roughly the same fashion each time. You can use a bottom of the barrel maiden claimer or a stakes horse. Doesn't matter as long as they are reliable to run similar races pretty much every time. Let's say there are 80 horse running on a card. Variant makers will find a half dozen who,no matter where they finish, run basically the the same number each time. They will make a raw or Zero time for the races those horses run.They don't have to win. In fact it's better that they don't since horses that win usualy run quite a bit faster than previous races. Ok. so now you've calculated your raw time. Adjust it for ground lost and wind. All six horses now can be assigned a raw speed figure number. If all six ran about three lengths faster than their norm you have a plus 3 track. 6 lengths slower a minus 6 track. Once you know you now have a accurate variant you can make a very good number for everyone who ran that day. A good variant is far and away the most important part of making speed figure numbers. Here's an example why. Me and Coach Pants are gonna race 100 yards at the beach for DT bragging rights. We line up and "WE'RE OFF" We fly our 100 yards in 10 seconds flat. ( in our dreams) and finish in a dead heat. But! Upon further review. I ran on the hard packed sand right next to the water. While Pants ran on the loose cuppy sand right next to the boardwalk. Even though we finished right together in the photo and our time was the same Pants should get the bragging rights because he will have run a much better race getting a faster figure. Reverse our lanes and he wins by many. Hope that helps.