Agreed that realism is required.
However I should point out that (based on the numbers) UA tend to be counter seasonal at MAN for some reason. Take January 2017 for example - 9,461 (91.4% lf).
Obviously within this, some days will be more popular than others. Even in the quieter summer months I would expect days where the flight is overbooked and days where it is very empty. Just the nature of the business.