[Harry_Gaill]

However, if you want to be really precise you could do it like this:

House: 1 Interior: 69 World: 1
House: 2 Interior: 69 World: 2
House: 3 Interior: 69 World: 3
House: 4 Interior: 45 World: 1
House: 5 Interior: 45 World: 2
House: 6 Interior: 8 World: 1
House: 7 Interior: 34 World: 1
House: 8 Interior: 34 World: 2
House: 9 Interior: 34 World: 3
House: 10 Interior: 34 World: 4

See what I mean? Houses with different interiors can still have the same virtual world as other houses, but if you use the same interior twice, or possibly some more times, use different worlds.