How to properly resize ContextActionService's buttons and position them?

Hi, I’m making a button to throw a C4 for mobile users. I have created it but I’m having a bit of trouble positioning it and resizing it. I need to be at the top of the Jump Button for all the mobile users, no matter which mobile device it is. Here’s my code:

contextActionService:BindAction("Throwing", onBind, true)

local button = contextActionService:GetButton("Throwing")
contextActionService:SetPosition("Throwing",, -70, 0, 10))
contextActionService:SetTitle("Throwing", "Throw")

Help is appreciated! Thanks!