Start with hard timing errors
Malformed timestamps and end-before-start cues can prevent playback or create obviously wrong captions. Fix those before style/readability warnings.
Characters per second is a useful heuristic
CPS approximates reading load by dividing visible character count by cue duration. It does not measure language complexity or viewer ability.
Long lines affect display
Very long caption lines wrap unpredictably on phones and players. Consider deliberate two-line phrasing at natural language boundaries.
A checker is not certification
Accessibility requirements vary by jurisdiction and platform. The report is a practical QA aid, not a legal compliance determination.