Attempt to compare number and boolean?

My code (this is only some of it)

WallSizeText.FocusLost:Connect(function(enterPressed, inputThatCausedFocusLost)
		if enterPressed then
			local Size = tonumber(WallSizeText.Text)
			
			if not Size >= 100 then
				game.ReplicatedStorage.ObjSize:FireServer(Size, game.ReplicatedStorage.PlacementItems.Wall)
			else
				WallSizeAsker.Text = "Limt is 100!"
				wait(3)
				WallSizeAsker.Text = "How big would you like your wall to be?"
			end
		end
	end)

I put 50 in the text box and I got this error: attempt to compare number and boolean I used tonumber but I don't know if I'm using it right.