Looking further into this, this is correct. The Axis won a Marginal Victory for capturing 200 Victory Points. The reserve points are then compared and since the Axis reserves are greater than 1.5x the Allie reserves, the victory level is increased by two to a Decisive victory. That's why the numbers aren't added together - reserves levels are used to tweak the Victory Reports results. (See sec 7.1 in the manual.)
Boku Strategy Games, Developer of Combat Command and Horse & Musket