This is the important part of the code
script.Parent.Text = plr.PlayerStats.MeleeExp.Value / plr.PlayerStats.MaxMeleeExp.Value * 100
I want to add a % symbol after this value
script.Parent.Text = tostring(plr.PlayerStats.MeleeExp.Value / plr.PlayerStats.MaxMeleeExp.Value * 100).."%"
You can use "tostring" to transform a value into text. Then, use ".." to add the percentage character.