It would seem than the UEE fleet number that appears in the rsi site is NOT the real number of backers, but the numbers of ships that people have bought. So the real number of backers (with paid accounts) is a lot lower than thought.
Found it on the elite forums
https://forums.frontier.co.uk/showthread.php?t=203785&page=43&p=3230651&viewfull=1#post3230651