NCBI location name

Question

[9521ljh]

I find somatic mutation

one of the genes is APH1A

But there are not one annotation.

ex.

APH1A:NM_001077628:exon4:c.T425A:p.L142H  
APH1A:NM_016022:exon4:c.T425A:p.L142H
APH1A:NM_001243771:exon3:c.T254A:p.L85H           
APH1A:NM_001243772:exon3:c.T215A:p.L72H

Question:

1. What is meaning 001077628, 016022, 001243771, 001243772 ?
2. Why exon number is different?

[Pierre Lindenbaum]

0) why is it flagged as 'NCBI' ?
1) accession number https://www.ncbi.nlm.nih.gov/books/NBK50679/
2) alternative transcripts