In there interest of simplicity - and these numbers are for hypothetical experience only.
Say it costs 45k to get This done now.
Community is prepared to cover 25k.
45k = X
25k = cX
45k - 25k = aX (or 20k)
So the ambassadors jointly cover aX (20k)
10 true ambassadors agree to fund.
trueX = 20k / 10 or 2000 PER AMASSADOR
X (45k) = cX (25k) - aX (20k/ ten ambassadors)