Select the Candle number and add to the cart. 

e.g. if you want to celebrate 16th Birthday, then follow the steps like

1. Select "1- One number" candle and add to the cart
2. Select  "6- Six number" candle and add to the cart

Similarly , if you want to celebrate 45th Birthday, then follow the steps like 

1. Select "4- Four number" candle and add to the cart
2. Select  "5- Five number" candle and add to the cart