How can a single peptide produce redundant fragments during mass spec proteomics?

Question

[N15]

I am wondering how a single ionized peptide can produce fragments offset by one amino acid, as shown in this figure:

For instance, if your peptide is ANELLLNVK, I could understand producing fragments ANEL and LLNVK for example, but how A, AN, ANE, ANEL etc? How can a residue be contained in another fragment if already encompassed in one?

This all started because I was wondering how mass spec proteomics can produce the correct directionality of a peptide sequence. It must be because each residue adds a known mass, thereby increasing the m/z and yielding the full peptide sequence.

This has been bugging me for hours and I must be missing something!

Answer 1

[N15]

Figured it out. More than 1 peptide gets ionized ;)