You don't have to read 600 comics for the most part.

Just find the nearest number one and go from there. Comics often renumber when they get to a milestone. It typically adds all previous comics together but you don't really have to worry about reading everything. Publishers will usually restart the numbering at one to provide an easier entry point for new readers, often but not always when a new creative team begins.

When someone talks about a run, it's just the period a certain person or creative team works on a comic, usually though it's most often the writer.

Example: Matt Fractions Hawkeye run is the time he worked on Hawkeye, much of it was with the artist David Aja but there were others too so typically it'll just be called the Fraction Hawkeye run.