Hi Alex,
As far as I understand AL150 license is for SAM and I don't think Nodes or Volumes are linked with this license type (149 Nodes, 149 Volumes). For Nodes or Volumes you would be rather using SL150.
Its just that your components are linked with AL150 (149 Components). And yes you can not exceed 150 Components when you are using this license.
Probably the count is considered for your active components not the once that have been unmanged.
Hope this helps