Follicle count

I've been on gonal f for 9 days and during my ultrasound today I had only 4 mature follicles (measuring approx 12 mm) and approx 12 follicles in total. The FS recommended I come back on day 12 (Monday) and they'll decide if I'm ready for retrieval. She said it's unlikely that the smaller follicles will mature enough. I'm seriously disappointed that I may only have 4 viable follicles. Has anyone else experienced this and did any more follicles mature? Thanks!