Remortgage capital value is greater than previous mortgages capital

Hey all. Feel like I need to check if this is normal, or if I've missed something somewhere along the remortgage process. Planning to speak to my solicitors tomorrow if this is not normal.

We applied for our first remortgage with a new lender 3 months ago. At that time the remaining capital of our mortgage was £150k. Now, 3 months later, we've completed. The capital of my mortgage with the new lender is £150k.

My old lender confirmed today that our closing capital balance was £149,300. So, the last three months of payments to my old lender have been for nothing?

Is this normal? I thought the new loan amount would be updated at the point of completion, and that we'd only get the amount that we owed. Instead we've basically taken out a (ever so slightly) higher mortgage amount.

I feel stupid that we've basically completed and I'm only just querying this! I had just assumed that the amount would get updated.. but was this an incorrect assumption?