Numbering continued from Dennis the Menace Giant (Pines, 1955 series) #6 (Summer 1958). Note that this series also starts with a #6, so two different issues with the same number exist. Numbering continued with #76 as Dennis the Menace Bonus Magazine Series (Fawcett, 1970 series).
This is really an umbrella title. Each individual issue has a different title in the indicia; e.g. #6: "Dennis the Menace Giant Christmas Issue", #7: "Dennis the Menace in Hollywood", etc.