text: So access is public, you don't have to register as a user previously, but only allowed for the handicapped, right?
  
  So according to this ( https://wiki.openstreetmap.org/wiki/Tag:amenity%3Dparking#Additional_Tags ) and this ( https://wiki.openstreetmap.org/wiki/Proposed_features/parking#Recommended_default_access_restrictions ) wiki page and section I would suggest
  access=yes
  access:role=no
  access:disabled=designated
  capacity=6
  capacity:disabled=6
  
  But currently the capacity is tagged as 4, if it is 6 like you said @Edelweiß, it should be changed!