Why are these voltage differences?

@johnyb98 shouldn't voltage be EXACTLY the same? No. The voltage listed is the nominal voltage and does not take the typical end-of-discharge and max charge voltage and other variable like ambient temperature etc. into consideration. That is why variations are absolutely normal. You do not know the state of the new battery vs. the old battery. Could it cause any damages? Not it it is within the parameter of your device (don't use a 12V battery on a 5V device;-). remember that even batteries are now smart devices. There are circuits that control over and under voltage (within reason) and the 2% difference in your battery most certainly will not do any harm to your system. Remember, you do not know the charge state of your battery. You are good to use that battery without any sequalae to your computer.