Transcript variants in the NCBI browser
 

I am wondering how they build up the transcript variant view in the NCBI web-page. For BRCA1 seems to have at least 5 transcript variant? How reliable this information is? Could anyone help?

I cannot post the link to the NCBI web-page cause I am new here. But go to the NCBI and find the gene information about BRCA1 of homo sapiens.