Hi Joe.
Sadly what the guys are telling you is correct.
Basically you have purchase a vacuum gauge with way to large a scale.
The more practical ones start at say 40torr or even 20 torr to Zero.
So basically I would use your one to observe the pressure drop then use the above to monitor the deep Vacuum.
Whilst in a deep vac you want to be able to observe small movements of pressure to help diagnose what is going on.
Your gauge is not wasted as I say it can be used to help prove the initial negative pressure drops.
Which can help when evacuating larger systems.
There is nothing worse than the initial doubts as to whether everything is leak tight.
So your gauge is not wasted, just not quite accurate enough to cover all the bases.
Grizzly