[AA] Less than max number Sims showing up at custom venues despite defined role

I set up a custom venue to have a number of different roles at different times, and no more than six sims will show up at a time despite me having roles for between 8-18 sims at a time. The roles that were actually filled were seemingly random from day to day. I only have one sim in my active household and my mods are disabled. Since it says I can have up to 20 sims at a time, I would expect at least 19 of those to appear on the lot. 

Example: 

9:00am with roles designed for 1 maintenance person, 1 music teacher, 1 music student, 4 customers, and 1 employee. I had a max of 3 customers, the maintenance person, employee, and music student one day. The next day, the employee didn't show up but the teacher did and still no 4th customer. 

5:00pm with roles designed for 1 chef, 2 wait staff, and 6 restaurant patrons. Day one had 1 chef and 4 patrons, Day two had 2 wait staff and 3 patrons. 

9:00pm with roles designed for 4 troublemakers, 1 DJ, 1 bartender, 6 clubgoers, and 6 flirty clubgoers. First night I had 3 clubgoers, 1 flirty clubgoer, and 2 troublemakers. Second night was 3 clubgoers, 2 flirty clubgoers, and 1 troublemakers. Neither of my staff-like roles showed up either night. 

Edit By Crinrict: Added Tag to Title, Adjusted Title