The notional unit's strength starts out at one. Rotterdam is a city, +1. It is not (any longer) next to a friendly unit. No shore bombardment. It's a Netherlands notional in a Netherlands home city, so it is in supply. It is surprised, -1. SoThe notional unit has 1 combat factor, modified by:
+1 if it is a city hex;
+1 if the hex is in the home country of the major power that controls the hex;
+1 if it is not stacked with a land unit, but is in the ZOC of a friendly corps or army;
+ the shore bombardment modifier for each invading unit;
-1 if it cannot trace a basic supply path of any length; and
-1 if surprised (see 15.0).
1 + 1 - 1
should equal 1. MWIF calculates zero.
Am I wrong, or is the program? When the Dutch corps in Amsterdam was still there, MWIF calculated the notional strength as two. Killing the Amsterdam corps should have reduced the strength to one, not zero.