CAD tip # 8161:

But there are situations when two licenses are consumed from your license server. This occurs typically when you make use of the free licenses of 3 previous versions of your software (one of the subscription benefits).

If you own e.g. a network license of Design Suite 2012 (with the previous versions support) and you run two older versions of your applications with the same version number (e.g. AutoCAD 2011 and 3ds Max 2011), they will consume a single older license (Design Suite 2011). But if you launch e.g. Showcase 2012 and AutoCAD 2011, they will take two license (these two applications do not share a common "product"). Also two licenses will be consumed if you run concurrently AutoCAD 2010 and 3ds Max Design 2010, as there was no Design Suite for the version 2010 (so these are two separate products).