Round to the nearest set range

You can use:

Q3: =DATEDIF(O3,TODAY(),"m")
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R3: =IF($Q3<MIN($F$4:$K$4),0,LOOKUP($Q3,$F$4:$K$4,INDEX($F$5:$K$7,MATCH($P3,$E$5:$E$7,0),0)))
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edit: modified per post #3