This service is to repair the Battery Gauge IC on an iPhone 8 or 8 Plus, if you want to know more details then please read on below.
The iPhone 8 can easily be damaged during a battery replacement, the reason for this is that the components near the battery connector are standing high on the board, all it takes is a finger or pry tool to pull these components from the board.
They need to be replaced to allow the phone to work once again.