Serv.L.Nat is calculated 100 * INVOICED / (ORDERED + DELAYED). For National Service Level the case statement (including the calculations) is as follows (the inner CASE limits the Serv.L.Nat per cust to a range of 0 - 100 %):
CASE WHEN "fact"."CustID" = 100001 THEN (
CASE WHEN Serv.L.Nat > 100 THEN 100
WHEN Serv.L.Nat < 0 THEN 0
WHEN Serv.L.Nat IS NULL THEN 0
For Export the sql is exactly like the one above, barring the reversed condition.
PS. The above is a burst of pseudoSQL so don't mind the typos, the actual code is tested to work as intended... barring the fact that something's wrong with getting the values to appear.