Scaling a Vector from Specific Anchor Point

I'm trying to make a power guage similar to Nanaca Crash.
I'm very new to this so I've figured that scaling a vector would give me the best result.
I'm trying to understand how to scale my arc vector from the bottom left corner so the arc grows out from a stationary right angle.
I've played around with the inspector settings to change any points, but that doesn't seem to work.
And I have no idea where to begin with code. Maybe some methods of Vector.
Here's a gif of what I mean:
https://imgur.com/a/FFr01GQ


I eventually want to correspond the lowest point to the value 1, and the highest to 100.
Get an input from the user, stop the animation, and get the value of where the meter was stopped,
then apply that value to an addForce.