her2 and chemo therapy

I was diagnosed with her2 one week ago. The "score" on my path report reads [quote] 3+ over 3+ [end quote]. I have had a lumpectomy; sentinel node biopsy scheduled but not done yet. I have 2 questions:
first: what does 3+ over 3+ mean...not familiar with the "over" part. And 3 out of "how many?"
second: One nurse told me that if I was node negative I would not need chemotherapy. A radiology oncologist said she thinks I should consider chemotherapy. Does anyone have any statistics or concrete evidence one vs another?
Appreciate any info anyone has. Thanks. Jane