In video games they commonly use that to mean they are multiplying by 25. We know it's not correct in stats. This is why game wikis commonly put the actual formula for things rather than the tooltip the developers wrote.

I feel they might've left something out. If you're at base value still an additive 100% increase (1+1=2) is better than a multiplicative 25% (1×1.25=1.25) increase but in games where bonuses stack another additive 100% increase would raise the effective value by 50% instead (1+1+1=3) whereas another multiplicative 25% would still raise the total by that much (1×1.25×1.25=1.56) so if you're stacking a lot of bonuses, eventually the multplicative ones are more effective. As for how many steps it would take to be equal in our example... 1+1×X=1×1.25^X I'm not gonna do this in my bed on my phone but that equation should already tell you that the right side grows faster when X -> infinity