Why is BRCA1 exon 4 not displayed in the CNV results?

There are two different BRCA1 exon naming conventions.

1) The BRCA1 legacy exon nomenclature is still used by some clinical databases, where exon 4 is missing due to an initial oversight during BRCA1 protein characterization – all following exons have a number increased by one.

2) The standard HGVS/RefSeq/Ensembl nomenclature ranks exons dependent on the specific transcript (NM_*, ENST*) and they are always numbered in increasing order from 1 up to the last exon.