How are season ticket sales calculated?

I'm beginning to think that this is a loosely fixed value, or based on local populations.

I'm currently managing Haverfordwest County in the Welsh Prem and am currently in my seventh season with them, 2018/19 season. In my first season at the club we sold 62 season tickets which, given that fact the club had a pokey old stadium, had a half-star rep and was in a one star league, didn't strike me as too odd. However, in the six complete seasons I have spent at the club I have:

- Increased club rep to 1 star, now highest in Wales.

- Upgraded stadium to 2000 all seater, from a 2000 half seating/standing arrangement. (Further seating coming next year).

- Increased club training and youth facilities two 'levels', up from essentially non-existent.

- Won the league six seasons running, with 3 domestic cups along the way.

- Increased average attendance for league games from ~200 to 750+.

- Qualified for the Europa League groups stages twice, currently in the Champions League group stages for the second season running.

- Increased the league rep to one-and-a-half stars, from one star, thanks to my European performances.

- ~130th in Europe based on coefficient.

- Sell out every home European game.

Despite this, the club sold 69 season tickets this season, only 7 more than my initial season and less than 10% of my average attendance.

Does anybody have an idea as to when I can expect to see this increase more than it has already (I think this is the main reason I can still only offer pittance to players for wages) or have any experience of what needs to happen before my fans take the plunge and snap up a season ticket?

I think geography/local population is a major factor. I created a club based in the Scottish Highlands but playing in the English leagues. My season ticket sales and attendances are consistently by far the lowest in my division, which is entirely right given the population and travelling distances for away supporters. It's a handicap we just have to live with.

They are calculated by every one sold counts as one.