A bit misleading, I think.  THere is no way you can burn fuel twice.  At best, it might be burning incompletely somehow at the bottom, then burning the remainder at the top.

I read somewhere, a long time ago, that "wood" does not actually burn, but rather, the heat gassifies the wood - i.e. it goes from a solid to a gas, then the gas burns.  You can kind of see that when a stream of gas shoots out of a burning log.

even gasoline liquid does not burn, it is the vapor that burns