Humans have been migrating and mixing for thousands of years. While your ancestors may have been from Denmark it doesn’t make them “100% Danish” and you 25%. And this is for several reasons. Your Danish ancestors were likely some combo of Scandinavian, Anglo, Germanic etc...

Another thing is all these “nationalities” that they have a part of their system are based off a limited population of people they have tested in those regions and they have been designated the benchmark for what it means to be “Western European”, “Eastern European” etc despite the fact that all of these places are the result of migration and mixing.

The test just gives you a very generalized ballpark largely based on their specific databases which explains why it would be vastly different on other dna testing sites with their benchmarks being totally different.