This comment is saying "the percentage of any given 200 programmers applying for a job that are, in the end, reasonably fit to do the job depends on the job being applied for".
If the job is a mid-level C++ programmer job at an insurance company, many more of them are likely to be good fits than if it's a senior embedded systems architect job at an aerospace firm.
If the job is a mid-level C++ programmer job at an insurance company, many more of them are likely to be good fits than if it's a senior embedded systems architect job at an aerospace firm.