Calling pricing routine in sale order

Hi,

I have a requirement where I have to modify a pricing routine 9XX for sale order. In pricing procedure, I observed that this routine 9XX is assigned to multiple pricing conditions (ZNN, ZMM, ZDD etc). I saw that this routine is getting called many times in debugging for each of these assigned pricing conditions. May I know on what basis this pricing routine gets triggered multiple times for the corresponding pricing condition?

Thanks in advance.

Regards,

Sri