Growing Times

Hi, all i have a few questions i need advise on first can anyone tell me when buying seeds from were ever they state for instance these seeds harvest in say 65 days does this mean from seed or from flowering stage. Second my tent is 90cms x 90cms x 160cms i have four northern lights growing which look good but what would be the recommended amount of plants for this size i am using ebb and flow with rock wool blocks in clay pebbles. Many thanks in advance