what does this header mean?

If I want to randomly pick 10 sequences (30 in length) from the .fasta file to generate another .fasta file for testing, what does mean by

"put the zero-based location of the mRNA transcript from where the read is taken" and ">NM_001008503.1:coordinate_of_read....."?

The file I uploaded is the sample .fasta file I am gonna use.

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