The amount of licenses your company is technically allowed to use would depend on how many of these seats have been upgraded from previous seats and if any are on Subscription. In addition, many of the products from 2007 (including LT) and all those 2006 and prior have been retired by Autodesk.
For example, if you had 100 seats of AutoCAD LT 2007 that were upgraded to AutoCAD LT 2010, then your 2007 licenses are no longer valid and cannot be used because they are now AutoCAD LT 2010 seats. To run then 200 seats of both AutoCAD LT 2007 and 2010 would be violating your license agreement. Should your seats be under current Subscription, then you will have been autofulfilled to AutoCAD LT 2011 and be allowed to run up to three versions back. This means that any current licenses under Subscription can legally be licensed to run as LT 2008, 2009, 2010, and 2011. However, you cannot run concurrently more licenses than are under Subscription. So again, if you had those same 100 licenses and they were upgraded under a current Subscription plan, you could run any combination of LT 2008 thru 2011 so long as there are not more than 100 licenses total being run at the same time. This could be ten of 2008, thirty of 2009, fifty of 2010, and ten of 2011... but no more. Running four-hundred seats concurrently would be violating your license agreement because you don't have a total of four-hundred seats between all the versions.
Any single licenses that have not been upgraded and are not under Subscription can continue to be run, however any product 2007 and older does not qualify for special upgrade pricing. There are exceptions to running legacy products, however the bottom-line is that you cannot run more licenses than you currently own.
I hope that helps.