How do you compare to the sites you lose to?
A score on its own is a number nobody has a feel for. 62 means nothing until you know the four sites you compete with score 71, 58, 44 and 80. Put your domain in, add up to four competitors, and every site is fetched in the same request and scored on the same rubric. Free, no signup.
How this is measured
Every site is requested inside the same call, so a network having a bad afternoon affects all of them or none. Comparing a score taken today against one taken last month is the mistake this exists to prevent.
A check that could not be measured for every site leaves the comparison for everybody. If one competitor's sitemap is unreachable, the sitemap checks drop out rather than scoring that competitor zero and flattering you. That is why the scores here are lower than each site's own audit score: they are recomputed over the shared subset only, and both numbers are shown.
The rubric is open source under MIT and published as data, so you can read exactly what each check does rather than take a number on faith. Run the full audit on your own domain for the fix list.