"LEAD SHIELDING VALUE" is NOT THE X-RAY GLASS THICKNESS, but the actual thickness of lead shielding required in the wall, partition, barrier or door as calculated by a radiation physicist for x-ray gamma protection shielding, and all Lead Backed Drywall, Shielded Doors, X-Ray Glass and Lead Lined Frames that occur within that same wall segment or area must meet or exceed this shielding value. The lead shielding thickness requirement may also change from wall to wall and room to room due to many additional factors.
Do you have a second x-ray window spec?
Do you have a third x-ray window spec?