Hi,
With longfills, only the base liquid and the booster (if I want) go in, depending on the ratio I mix it to (DL or MTL). I think.
The case of aromas is different; there it’s obviously worth considering the manufacturer’s recommendation, but if it’s too much, as others have written, you dilute it. Mix a smaller batch first and then you’ll feel it. Help with mixing: https://diy.vaperina.cc/
A shortfill is already a finished product; you can at most boost it or top it up with another 10-20 ML of base liquid, depending on the manufacturer’s mixing ratio (usually 50/50 for MTL, 70/30 for DL). You don’t need to calculate percentages there.
(Of course, you have to calculate a bit, because sometimes I only have a 50/50 booster at home for my 120 ml 70/30 mixed longfill, so I calculate what ratio to put it together in.)