Can I use Self like?

Hey devs! I want to learn how to use Self. But nobody can anwser this question, so I make my tests.

I want to know if this goodway. ServerScript

local FixStat = 100
GameSetting:ModifCash(function(self) -- I know this can be changed by another variable
    self.TextLabel.Text = '+$'..GameSetting:ConvertShort(FixStat)
end)

ModuleScript

function ModifCash(f)
    local BillboardGui = inst('BillboardGui')
    BillboardGui.ExtentsOffsetWorldSpace = vec3(0, 5, 0)
    BillboardGui.Size = ud2(1, 0, 1, 0)
    local TextLabel = inst('TextLabel')
    TextLabel.TextColor3 = cl3(1, 1, 1)
    TextLabel.Size = ud2(1, 0, 1, 0)
    TextLabel.TextScaled = true
    TextLabel.Transparency = 1
    f(BillboardGui)
end