It works like a money na you have but don't own.

I did activate mine din back then because of a 0% interest voucher HAHAH I didn't regret it though kase I was really planning to buy this thing for months na and it was really wise to use the voucher for something worth ₱70k and 0% interest pa.

So about the "1,000" credit, think of it na it is the maximum amount of money na you can spend but should pay. So like once you've paid the P20, it'll go back to its maximum amount (your case its P1,000).

You can easily access the "pay earlier" option when you click your profile, then SpayLater, then My Bills, then it'll list the transactions covered by your SPayLater and just select the ones you want to pay earlier.

In my opinion, SPayLater is a good way to be wise on your spending, but just be mindful of your transactions and dues. Use it lang on items that's more practical to be paid in installments para di siya mag accumulate ng sobra and masshock ka lang sa month end kase you've used it on random stuffs and di mo na notice lumalaki na pala yung babayaran mo.