"Super efficiency" is marketing jargon. Ideal seem to have adopted it some years ago. They had an "SE" range of boilers for example. Recent Ideal boilers seem to operate in two modes "High efficiency" and "Super efficiency" and some models display the current mode on the display.
My best current guess is that your 22% is the fraction of time the boiler has spent in SE mode. It seems to be averaged over a fairly long time, possibly since manufacture or the last reset.
Exactly what Ideal mean by 'super efficiency' mode is not clear to me. There are a couple of plausible possibilities but I'm currently leaning towards "condensing", i.e. the return temperature is below some threshold such as 40°C and the system is working at optimimum efficiency.
Anyway, as I wrote above, if you want to know the efficiency of your boiler you need to monitor the return temperature and it can be calculated from that. Even if your return temperature is always above 55°C and your boiler never gets into condensing mode its actual efficiency will still be around 80% or more.