=INDEX({"high","medium","low"},1,MATCH(A1,{500,50,10},-1))
This will return;
“high” if A1 is between 51 to 500
“medium” if A1 is between 11 to 50
“low” if A1 is below 10
BTW, why not use a Dynamic Named Range for the chart?
Excel LOS base on VC ratio
=INDEX({"A","B","C","D","E","F"},1,MATCH(K2,{0,0.35,0.58,0.75,0.9,1},1))