fr: neutral grid but half distance for buy 1 sell 1

let's imagine the grid seg is 0.5, the present conduct is buy 1 at x-Zero.5 and promote 1 at x+Zero.5. i want a tighter model the place the purchase 1 is at x-0.25 and promote 1 at x+0.25, purchase 2 at x-Zero.75 sell 2 at x+Zero.75 and so on