Your first payment is larger for two reasons: your second payment is Split Pay's share of your bill — it starts at 30% — and your first payment includes the Split Pay fee ($9.99 plus 1.5% of your total payment). Whatever's left of your total bill, plus the fee, is your first payment.
Example:
Your rent is $1,800
Your second payment is $540 (30% of $1,800)
Your first payment is $1,260 (the rest) plus the fee — $9.99 + 1.5% of $1,800 ($27) — so $1,296.99 total
The fee is always part of your first payment. It's never charged separately at a different time, and it's never added to your second payment.
The good news: every month you pay your second payment on time, Split Pay's share of your bill grows by 5% the next month — and your first payment shrinks proportionally. Over time, it gets closer to a clean 50/50 split.
So if you're at $540 / $1,260 now, next month you could be at $630 / $1,170. Keep paying on time and it keeps growing until you hit an even 50/50.