From last year, to give an idea of how they probably intend on enforcing the limit:

But the most stringent part of the plan came into force on 1 January 2020, when these areas must slash their public housing stock to no more than 40%. To achieve this within 10 years, entire blocks will be emptied and converted into private and co-operative housing, from which people on low incomes will be barred. In some cities (though not Copenhagen) the blocks will simply be demolished.

Current tenants will be offered alternative accommodation, but no control over its location, quality or cost. Those who refuse can now simply be evicted. Adding insult to injury, the eviction and renovation plans will be paid for from proceeds from a fund paid into by public housing tenants themselves.