As an institution, you can activate an option to limit the number of requests a student can make for his or her placement. By default, if you don't activate this option, students can submit as many requests as they like. Once you activate the option, all students at all institutions will be entitled to the same number of desiderata days.
Step 1: Go to the "Institution settings" tab on the "Options" page.
Step 2: At the bottom of the page, in the "Institution options" category, activate the "Limit the number of desiderata that can be sent per placement" option.
Step 3: Click on the edit button to determine the number of desiderata days available to students.
Step 4: Indicate the number of days you wish to allocate and click on "Ok".