Ok.. for simplicity let's pretend that glow fuel only has 3 ingredients: nitro, oil and methanol. Oil content must remain basically constant in all the fuels, otherwise any fuel with a reduced oil percent would ruin the engine. More nitro = less methanol.

I'm bored, so here's the algebra:
We'll do.. nitro % + oil % + methanol % = 100%

So for a fuel that's 10% oil.. 15% nitro would mean:
15+10+x=100
25+x=100
x=100-25
x=75 (% methanol)

10% oil, 30% nitro:

30+10+x=100
40+x=100
x=100-40
x=60 (% methanol)

You get the idea, I hope.