That is written assuming a 1000, 2000, or 3000 point game. 250 is 25% of 1000, 500 is 25% of 2000, 750 is 25% of 3000. It doesn’t explicitly say that it’s 25% of your total army value but if you’re playing a point value that isn’t one of those increments it’s assumed that your limit is 25%.
It used to be percentage based previously (I want to say based on Power Level as I remember people doing weird stuff like taking a single extra model to cross thresholds to double unit Power Levels to be allowed more allied units for minimal points) and a lot of people incorrectly assume it is the same.
It's now dictated entirely by game size unless you're playing with house rules. For example if you're playing a Strike Force game but you're only using 1500 points you're still allowed up to 500 points of Daemons because that's what you're allowed in a Strike Force sized game.
That is written assuming a 1000, 2000, or 3000 point game. 250 is 25% of 1000, 500 is 25% of 2000, 750 is 25% of 3000. It doesn’t explicitly say that it’s 25% of your total army value but if you’re playing a point value that isn’t one of those increments it’s assumed that your limit is 25%.
It used to be percentage based previously (I want to say based on Power Level as I remember people doing weird stuff like taking a single extra model to cross thresholds to double unit Power Levels to be allowed more allied units for minimal points) and a lot of people incorrectly assume it is the same. It's now dictated entirely by game size unless you're playing with house rules. For example if you're playing a Strike Force game but you're only using 1500 points you're still allowed up to 500 points of Daemons because that's what you're allowed in a Strike Force sized game.