You have to manually calculate the point height until the slopes are the way you want. Put the annotation on to see how it changes. I assume you want to aim to have at least 1%, or 2% etc. to the drains.
For complex floors with multiple slopes and distances, it may be good to limit the annotation to 1 or zero decimal points since it may not be possible to get exact 2% instead of 1.99%.
The floor you model won't be 100% like a contractor actually pours concrete. so make sure you make the intent clear.
Good on you for actually putting this on plans. Most plans i see don't show the slope and write in the specs somewhere to have a slope. The actual slab then is flat, with often even some slope way from the drains. Don't rely on contractor to automatically applying common sense. Definitely talk to the foreman before they pour the concrete so they understand what is expected.
Revit version: R2025.3