How to convert the offset to scale when used :GetTextSize()

I’m attempting to make a conversion for my background, which is resized by offset, but I can’t seek for a method that applies a good way of converting the offset into scale, when applied by :GetTextSize() - how can I do this so it fits for all devices? Here’s the code I’m using:

local textSize = tx:GetTextSize(title.Text, title.TextSize, title.Font,, math.huge))
black.Size = UDim2.fromOffset(textSize.X + 15, textSize.Y + 3) --needs to fit all resolutions, and the current size is {0.398, 0},{0.484, 0}

Expected result (from computer):
Unfixed result (from phone):
The issue is that on phone, it’s wider, and doesn’t fix perfectly as intended within the computer one (offset).