AAU = Alpha Acid % (On hop Package) x Weight of hops (ounces)
A recipe calls for 10 AAU of Cascade
Your cascade says it's 5.0%, so to get 10 AAU, multiply the 5 by 2.
You need 2 ounces of cascade for that hop addition
if your hops were 4.0% you would need 2.5 ounces, if the AA% is 6.0 then you need 1.67 ounces.