The first burn is the most important as it’s sets the burning memory. So, in order to get the best burn possible, the first time you light the candle please burn until the pool of melted wax reaches the edges. Never move whilst lit or until the wax hardens.

The candle is made with a self-extinguishing wick. This means they will go out just before they reach the bottom and will leave some un-melted wax.
This is a design feature to stop the bottom of the candle getting too hot.
Don’t worry, you will still get the full burn time by the time it reaches this point.