Primedice can predetermine the outcome of a bet as much as you can, none. They don't know your client seed ahead of time, just as you don't know their server seed ahead of time. Your rolls are generated as soon as you load the page, and every time you reload the page, or change your client seed, the rolls change.
They do know the client seed unless I change it every bet. If I pick "1" as my client seed and don't change it for the next bet, it magically changes to 1-0001. Then the client seed for the next bet is 1-0002. Now this wouldn't be a problem if the server seed would stay the same.
When you set the client seed to "1" and then place a bet, the client seed doesn't change, when it goes from "1" to "1-0001" it is just showing you how many bets you have made on that seed, the seed is still just "1" therefore the client seed does not change from what you set it to.
Well I just ran the code on the verification page with bets I made yesterday and the extra -#### is part of the client seed. Its a fact.
Yes that is correct. 2 out of 3 parts are variables.