The rules general rules for conditional admittance are stated at the Stockholm university webpage.

It is also good to be aware that you can only be accepted to a maximum of 45 ECTS credits, and if you get conditionally accepted to a course the course credits will also be counted.

So if you get conditionally accepted to a course of 30 ECTS credits, all courses you have put on lower priority that are bigger than 15 ECTS credits will be removed.

If you cannot show eligibilty to a course to which you are conditionally accepted, you cannot be registered to the course.