No. 15 is good no. but not in respect of 4 & 8.for example the film Daud comes on 15.but was released on 22(4) aug. 97.& film Hisss also comes on 15.but released on 22(4) oct. 2010.both the films released on no. 4.& thats why bombed badly on box office.krrish also comes on 15(6).but was released on 30(3)th june & it was blockbuster.