The figures in that chart aren't correct (for a start the Leeds average stated is 250 more than their own programme says). Newcastle will be highest without doubt, followed by us and then Leeds.
The Football League tend to release their own 'official' stats for the previous season around January each year and looking at last season's Leeds were top with an average of 2,829 and have been in each of the last five seasons. Interestingly their figure of 3,045 in 13/14 was the only time a club has passed the 3,000 mark in the last five years and this season we're going to see three clubs with 3,000+.
Irrelevant but Small Heath's averages from 2011/12 to 15/16 were 1,489, 1,161, 1,293, 1,526 & 1,841.