Thanks , will doAs you can see from the answers in this thread, we never got to the bottom of what that number meant, if anything. I'd ignore it if I were you. If you're worried about the 'efficiency' of your boil attach a thermometer to the return pipe and check it's below, about 50°C. If so, all is well.
Also support told me that as my central heating has not been on since May that my efficiency level would show as low anyway. Total BS as this was showing same in March and before.
When it was fist installed 18 months ago I recall it was 60%+ showing so something is clearly awry but Ideal are not interested.