Two ARKs are generated upon creation of a new resource, and then another each time it is modified and saved. Here are the steps to replicate:
Go to staff interface
Select Create > Resource
Fill in the require fields, select publish checkbox, and Save
View new resource (not in edit mode)
Copy the ARK displayed in Basic Information
Paste that URL into a new browser tab and press return. It should redirect to the PUI page for the resource
Paste the same URL in a new browser tab but increment the number at the end of ARK, then press return. It redirects to the same PUI page for the same resource
Back in the staff interface, edit the resource again, save i
Paste the ARK URL into a new browser window but increments by two. Again, it redirects to the same resource (unless another record has been created/edited in the meantime.)
For example:
http://test.archivesspace.org//ark:/99999/1073
http://test.archivesspace.org//ark:/99999/1074
http://test.archivesspace.org//ark:/99999/1075
All redirect to: