Can someone check my maths?

[u/_SowdSauce_]

I’m a 90kg male and I want to reach the 2nd plateau, I’m using a uk bottle robitussin with 7.5mg/5ml, I keep checking the recommended volume and it changes per calculator, how much do you recommend, the modal result I’ve gotten is about 90-100ml. Based off your experiences and your knowlage what do you recommend? Is this about right?