hey yall i need advice on how to take reta

im getting 10mg or 20mg reta and bac water, either 3 ml or 10 ml as an option

i just need the calculations for how much i should draw to make the dose 0.5 mg per week

also will that one vial only be used once or can i get multiple doses out of it? i have no clue. i’ve done my research but it’s still a bit confusing ngl

ps ive got a decent physique all bulked up js need to get this fat out