Only 25 units Gonal F?

Samantha • 23yo. TTC #1 for 4 years. PCOS. Blissfully married. Hoping our family is going to start with our first IUI cycle.
My follicles stopped growing after using 100mg clomid. They are stuck at 12mm so my doctor prescribed 25 units gonal f at night.  I know 75 units is the standard starting point. Anyone start so low? I'm confused.