Ok, I now understand how the preset box works.
In the attached pic, if u highlight the 'standard staking', that will lay to the liability of the preset stake. (50) in this case.
If I highlight the preset area, and want to lay for liability of 1000, is that not possible?
It seems to send a flat stake of 1000, whatever combinations of boxes I tick/untick.
The purple place, the most viable alternative to the Betfair exchange