Thanks JCL, i knew it was simple
So the second example would simply be a 12 minute bar that starts 3 minutes ahead of the standard 15min bar period... Basically it's a customised bar, and you can do this with any figures to suit your strategy?
This is cool, and for some strange reason the backtesting results are much better with the second version.
Would you encourage this non standard way of picking Bar Periods and OffSets if the backtesting results significantly increase?
Thanks again for your help and for Zorro