I'm I where I need to be?

Hello I just started phlebotomy recently. I've been fully trained and on my own for almost 3 months. I work a short shift and only see 20-30 patients a night. Like clockwork I've been getting two misses almost every night. Is this a normal ratio or am I falling behind? I don't have context for what 'normal' is and I just want an accurate assessment of how I'm doing.