From https://www.11v11.com/teams/bristol-rovers/tab/stats/option/attendances/ these are ALL of the 10K+ attendances they have had in the previous 11 years (data on that page excludes current season and seems to only go back as far as 2007)
11,883 - 14 Sep 2007 v Leeds United
11,750 - 30 Apr 2017 v Millwall
11,448 --27 Oct 2009 v Leeds United
11,200 - 26 Dec 2016 v Coventry City
10,557 - 28 Jan 2017 v Swindon Town
10,293 - 07 Mar 2009 v Leeds United
10,093 - 31 Dec 2016 v AFC Wimbledon
10,088 - 01 Nov 2016 v Fleetwood Town
10,053 - 14 Aug 2016 v Oxford United
10,029 - 14 Apr 2018 v Blackburn Rovers
10,014 - 01 Jan 2018 v Portsmouth
So including their 10K against their "best chums" Sunderland this season - They have had a dozen 10K+ attendances in that whole period, and the best season they had was 2016 when they had four.
Bear in mind also that two of the fixtures were against Leeds (great away following, novelty for the gas to play a big club) and four of them were Christmas home fixtures, and it puts into context how sad and pathetic their support really is
... and they think they could average 50K over five fixtures.