It is based on simple order of operations, using your example your Edge never reaches 8 ... start at 6, spend 1 (now 5), then gain 2 (now 7).
Right, but it effectively gives a pool of 8.
I am more interested in something like this:
High init, 6 edge to start, 2 major actions.
1) Spend 4 edge to target everyone (probably limited based on reaction but whatever) with full dice pool (before any opposed tests occur) Edge now down to two.
2) Gain Edge based on opposed tests. Edge now up to 4
3) Shoot at everyone
4) Get 2nd attack
5) Spend 4 Edge to shoot at everyone with full pool. Edge now zero.
Edge never went above 6 but you effectively got to spend 8 Edge.
It seems like a fast gun bunny could probably attack everyone within range with his full dice pool - twice before they even get to act. Since it sounds like 6e is more lethal lots of fights could be ended by 1 fast gun bunny.