Congrats on the PRG! The NPSL took me a bit to figure and if you've had an AmEx charge card before disregard this, but if not this might help.
With the NPSL AmEx says your "soft limit" fluctuates based on your history with AmEx. For my PRG it was very specific.
The "spending power" was always equal to 3 times the amount of my largest payment in the previous rolling 6 months. This applies to a single payment, not multiple ones to equal a monthly bill.
Sample Payments: Mar $500, Apr $450, May $1500, Jun $0, Jul $500, Aug $25 ----- if I hit the spending power button today (Sept) it would return "you're Approved up to "$4,500" (In the last 6 months $1500 was the largest, so $1500 x 3)
It's a rolling 6 months so it would stay at $4,500 until December assuming no more payments from Jun to Dec were greater than $1500. As soon as I made a payment greater than our sample $1500, it would recalculate to 3x that greater amount.
I wanted to know how this part of the NPSL worked quickly to avoid being declined a charge while I was out and about. Knowing this, I never had a declined charge. YMMV, but thought I'd share. Congrats again!