what does an R 4 B level of concern mean on a breast sono

I recently had a breast sono to confirm what the mammo saw and have to go for a biopsy. The report shows level of concern as R 4 B. what does that mean? is it good or bad?

[Cleveland Clinic]

Dear cassie500:  There is a grading system for classifying ultrasound findings that parallels the BIRAD scale used in interpreting mammograms.  A rating of 4 would be given to a suspicious looking abnormality, not characteristic but has reasonable probability of malignancy and a biopsy should be considered.  

[japdip]

A BIRAD 4 means a suspicious abnormality is observed and requires further investigation (biopsy); which you state you are scheduled to have. I believe it is stated that 25-50% of BIRAD 4 ratings can be something OTHER than a malignant finding. The biopsy is the only way to tell if it's (as you say) "good or bad". Best of Luck