Complex Tables which need to also do math on results?

I am working on one of the classes and came across the first "rollable" table reference. I immediately got how to do most of it in theory but I was stuck with one issue. It says:

"Roll 2d12 to determine the number of followers. Determine the class of each in this order: half of the total will be Fighters, a quarter of them will be Clerics, one-fifth of them will be Magic-Users, and if there are over 20 followers, one of them will be a Neutral-aligned Thief.
The followers will be at least second level; for each there is a 25% chance to add 1d4 to the base second level. Also, for each of these followers, there is a 2% chance that the follower is actually a highly unusual type instead of whatever the dice originally indicated. Roll 1d6 as follows:"

The x% chance things are easy, use as percentile or convert to other formats with same percents.
But what do I do when it says, exactly 25% should be X and 15% should be Y?

"A More Complex Example" showed me about how to make tables do more and I would use this as the starting point when I go to work on this. (Feel free to point me at existing mods or rulesets where I can see more examples to learn from)

I know I could code this in a lua file, but wondered if could do using the table functionality. I haven't looked into yet (I'm a breadth-first guy when learning and overeager!) but I wasn't sure how I would stick in "math" in addition to random dice rolling.

For the moment, it is just "text" instructions on one of the class-ability popups. Figure will address it when get to ability handling.

You could allow some more randomness and roll another d20 and 1-10 will be fighters, 11-15 clerics, 16-19 magic users and 20 a thief...
You would not get exactly the right numbers but nor would you with 2d12 followers...

There isn't really a way to do this since everything that follows depends on the first die roll, and by my reckoning if you roll anything other than 20 then the rest doesn't really follow properly. On a 2 you'd have 1 fighter and half a cleric 0.2 magic users and 0.3 left over. You aren't going to get a proper result until you reach a number which is divisible by 2, 4 and 5 - which I think is 20.

You could set up a table with the classes in the appropriate percentage and then call that 2d12 times from another table but that doesn't give you the correct result either.

You could use a story template to work some of the figures out based on a few tables but again none of it would be idea.