Why is my battery not fully charging?

I just replaced the battery in my Samsung Galazy S7 with the iFixit battery and kit. It was a 3000 mAh battery, but looking at the Accubattery app shows it is only charging to 2500 mAh. I calibrated the battery by charging it to 100% for a few hours, discharging completely, and recharging. Can anyone help me understand why this would happen with a new battery? Thanks!