I will assume like that,
In game over layout,Make another Global variable called totalcoin
Webstorage Local key "Coin"exist -Set total coin to webstorage.LocalValue("Coin")
Coin>totalcoin - set totalcoin to coin
trigger once, - Webstorage Set local key "Coin" to ""&totalcoin
-Set text coin to Your total coin is: & Webstorage.LocalValue("Coin")