Epever Tracer BN set to 14.8 volt, but shows up to 15.2 volt on MT50 display

[wd73]

I have the 30A version of the Tracer BN series, and use it to charge a 12V, 210Ah calcium-calcium battery bank (2x105Ah parallel)
Calcium batteries need a charge voltage of 14.8V, so i've set the Float and Boost voltages to 14.8 volt (and no equalisation)
However, when charging, sometimes the display of the controller shows 14.9 or 15V, and short peaks (few secs) up to 15.2 volts.
That's weird, since i set the charge voltages to 14.8 volt..
Does anyone know what's going on?

 

[wd73]

[EDIT]
I have to correct myself here; I set float voltage to 13.8v, not 14.8v (however, bulk charging is set to 14.8v)
[/EDIT]