Now, from the manual
1.9.1 defensive anti-armor strengths
Defending units benefit from increased Anti-Armor Strengths in
some terrain or Deployments. Effects are not cumulative. Only
the strongest modifier is in effect:
In a Fortified Line hex (any Deployment), or Fortified Deploy-
ment (any terrain): x5
Dense Urban, Dense Urban Ruin, or Mountains (any Deploy-
ment), or Entrenched Deployment (any terrain): x3.5
Urban, Urban Ruin, Bocage, or Marsh (any Deployment), or De-
fending Deployment (any terrain): x2
1.9.2 defensive anti-personnel strengths
Defending units benefit from increased Anti-Personnel Attack
Strengths in some terrain or Deployments. Effects are not cu-
mulative. Only the strongest modifier is in effect:
- In a Fortified Line hex (any Deployment), or Fortified Deploy-
ment (any terrain): x4.5
- Bocage (any Deployment) or Entrenched Deployment (any ter-
rain): x3
- Mountains (any Deployment), or Defending Deployment: x1.5
1.9. defensive strengths of vehicles
Vehicles in defending units benefit from increased Defensive
Strengths in some terrain and Deployments. Effects are not cu-
mulative. Only the strongest modifier is in effect:
- In a Fortified Line hex (any Deployment) or Fortified Deploy-
ment (any terrain): x3
- Dense Urban or Dense Urban Ruin (any Deployment) or En-
trenched Deployment (any terrain): x1.5
1.9.4 defensive strengths of infantry
Infantry and non-static weapons in defending units benefit from
increased Defensive Strengths in some terrain or Deployments.
Effects are not cumulative. Only the strongest modifier is in ef-
fect:
- In a Fortified Line hex (any Deployment) or Fortified Deploy-
ment (any terrain): x8
- Dense Urban, Dense Urban Ruin, or Badlands (any Deploy-
ment): x4
- Urban, Urban Ruin, Bocage, Dunes, or Mountain (any Deploy-
ment): or Entrenched Deployment (any terrain): x3
- Forest, Jungle, Hills, or Wadi (any Deployment), or Defending
Deployment (any terrain): x2.0
First screenshot: It´s a fortress hex, AT bonus 500%, Ap 800%
So, it appears here that the AT 500% level corresponds to the anti-armor strength to the unit, while the 800% should be the case for the infantry in the unit, not to the unit itself.