I've a pattern for loading bots into roboports (thankfully, we can now read the numbers), and that, for the main base, has a constant comb with the numbers of bots I want (two items in it, construction and logistics bots) and two arith combs to calculate the number of bots of each type I still need, which then set a requester chest.
But for an outpost, I don't want to be that elaborate, so just one arith for construction bots would suffice. Only... I need arith and const comb, because I cannot code "N - number of construction bots" with just one arith comb. I could code "number of bots - N"... and then negate this with a second arith comb.
And the combinators are too big anyway...
