Not sure if this will help but here is what I am working with.
A B C D
RISK ISSUEDETAIL CREATEDON Days Past
HIGH Service Req 12/23/2013301
SEVERE Service Req 3/25/2013574
CRITICAL Service Req 10/13/20147

Column letters are actually different than shown above and the High, Severe, and critical in this example is not reflecting the 45, 30, and 15 days being "removed" from the calculation in Days Past column. Also since the critical entry was created on 10/13/2014 the expected completion is within 15 days of that and should reflect a -8 since there is 8 days left to have it done.
The Severe has a 30 day expectation and since it was created on 3/25/13 it reflects a positive number since it is 574 days since it was created but does not show the "free" 30 days (actual display should be 544 days).
The High should be 256 days past accounting for the "free" 45 days.