What is a numerical value in admission application context?
My understanding is that they want to know how much of the total workload of your degree was dedicated to the topic of computer science. You're relatively free to choose in which way to quantify this workload (e.g. total number of hours of the courses on computer science), but since you're in Europe, my suggestion is to use ECTS: you may be able to get the amount of ECTS credits for each course directly from your university student's guide.