Performing a Full Data read is different from a regular data read in that it also includes reseting the clock of the HM-6. This is helpful in some cases where the clock of the HM-6 has stopped for some reason.
From the Monitor List, select the monitor you would like to read. For example, tap on this one:
Then select "Read Data" from the menu.
The app will perform a read and then set the time on the HM-6.
To verify the time on the HM-6, perform a "Live Data" and view the time on the top of the screen, next to the serial number: