Use IF and nested IF logic

I have employee scores in column B and I need a new column C that classifies each as 'Low' for scores <60, 'Medium' for 60–79, and 'High' for 80 and above using IF and nested IF logic. Implement the formula in C2 and fill down for 500 rows on the sheet Performance. Label C1 'Rating'.

Before I share Performance with HR, make the IF logic transparent and reduce reviewer hesitation. Add the rating in column C using nested IFs, include a comment next to the header explaining the thresholds, and create a small legend at the top showing the number of Low, Medium, and High. Also flag any out-of-range scores (below 0 or above 100).

I created a Ratings column with nested IFs for Performance, and HR now says thresholds may shift mid-cycle. I don't know whether to hard-code thresholds or make them reference cells. If I change to reference cells will it break existing formulas or reporting? What's the safest immediate change so thresholds can be adjusted without reworking downstream reports, and how should I communicate the change to HR and payroll?