See the screenshot inside spoiler tag, it might help.
I'm not sure which part you don't understand.
"desire" is the value defined as the lowest value chosen between two values. One of these values are "50" and the other is "your receptionist notoriety multiplied by 5". Then "desire" is used to see which actions would suit your notoriety more.
EDIT: I think I was kind of wrong. I'm not good at javascript so I did a little bit of research about Math.randomInt method. It generates a value between 0 and specified value, in this case it is your receptionist notority multiplied by 5. So what this means is, if you have lets say 20 notority game would get a random value between 0 and 100 then it will compare it to 50 and decide which is lower. Lets say game generated "40" as a random number. Since 40 is lower than 50 it will be the desire value. After those calculations since desire is not 50 and it is greater than 30 visitor will request a handjob. I think that's how it works.