Full details of the series appear on the web page for the first cache in the series, GC3XFMN Bravura 1 - Burnt Out.
To find the bonus you will need to collect the six values A to F from the 8 caches - each is repeated at least once so that you will still be able to locate the bonus even if you cannot find one of the caches or if it goes missing. Two codes are written in this cache's logbook and elsewhere on the cache.
Don't forget to note down the numbers for the bonus before you move on.
This cache is brought to you by Frango & Chips.