Length of the amplicon after trimming

Hi!

I have illumina myseq 16s rRNA amplicon reads 300bp length with 17 bp primer. After trimming length of this amplicon must be 283 bp max. BBDuk says that out of 300k sequences 298k were trimmed. Some sequences length is bigger that 283 bp. I wonder what these sequences are? Some sequences have for example 290 bp after trimming. Is it possible to amplificate sequence from part of the primer?

Thank you.