Understanding mortgage repayments

I’m pretty new to property ownership and I’m trying to understand my mortgage repayments.

I’ve done calculations on a few different websites and they’re spitting out similar numbers, but all are far from what I thought they would be.

My current mortgage is $645,000 at 6.69% with an LVR of 92% and currently interest only for a couple more months.

With a 30 year loan term, should my monthly repayment (to start off with) be $5,555? This being $3,762.5 of interest and $1,791 of principal?

The bank calculators I’ve used are spitting out figures around $4,500 in monthly repayments.

Any info would be greatly appreciated.