Thread Allocation

Hi, all,

 I have a GTX295 which has two 30*8 core GPUs. I set gridDim as 4 by 768 and threadDim as 258 by 1; I used  "info cuda threads" command in cuda-gdb and found that the threads allocated to my kernel is from <<<(0,0),(0,0,0)>>> to <<<(1,22),(255,0,0)>>> which is only around 90 threads. Is it possible to increase the number of allocated thread? Thank you very much.