It sounds to me like this number indicates broad success.
The rough estimate seems to be that only about two per cent of border crossings use an eVisa anyway (British passport holders don't and non-immigrating visitors don't).
Even over summer that would probably only mean maybe 2.5 million border crossings, so the other uses are not at the border — they will instead be employment/landlord/benefit/healthcare checks using the online systems.
So for example, renting a new property, starting a new job, applying for a new benefit, or needing non-emergency healthcare etc.