I expect that the OP has a London to Manchester Off-Peak Return, or similar. It is restriction code 9I and is valid via Sheffield. EMR obviously only considered their own off peak tickets when constructing that graphic.
What you've got to bear in mind is that an Off Peak on the WCML is equivalent to a Super Off Peak on the MML and ECML, as the latter two introduced "Business Saver" type tickets which became the Off Peak, whereas VTWC preferred to do that sort of "peak smoothing" using Advances (for which they indeed invented the forerunner of the modern-day Advance, the Virgin Value Single) so they never went for a second level. Just recently they have introduced Super Off Peaks on a few specific flows (mostly those where LNR is caning them) but those are very heavily restricted, typically not valid in the morning at all and with a very wide evening peak period and in some cases weekend restrictions.
This is another case where simplification did nothing of the sort. If these tickets had remained called Saver (for the general regulated off peak ticket with morning and evening restrictions, but not unduly swingeing ones), SuperSaver (for the really cheap ticket with swingeing and possibly weekend restrictions) and Business Saver (for the one with some peak restrictions, but quite loose ones) people would have known what they were and this inconsistency wouldn't really have arisen.