The market allows you to pick and choose the jobs you want to do. Many jobs have flexible ranges in which you can complete them. When you see a job you want to do you can accept it and schedule which day you will complete it.
There is a daily limit of 20 jobs that you can reserve or accept in advance for each day. Once you complete or cancel one you can accept another.
There is a total limit of 100 jobs you can reserve or accept in advance across multiple days. Once you complete or cancel one you can accept another.
These limits do not stop you from completing as many jobs as you like in a day. You can still complete over 200 jobs in one day if you want! You are just limited to how many you can add to your accepted list in advance.