The authority have a fundamental problem in that they fail to understand and use the mandated 28-day period in all of their letters.
And whether an owner is 'detrimented' (aaagh!) don't enter into it. '28 days from' is glaringly wrong and as they've used this in the NOR should ensure you win on procedural grounds alone:
6) If the enforcement authority does not accept the representations, its decision notice—
(a)must—
(i)state that a charge certificate may be served on the recipient unless within the period of 28 days beginning with the date of service of the decision notice—
(aa)the penalty charge is paid, or
(bb)the recipient appeals to an adjudicator against the penalty charge,
NOT 28 days from.
These differences are not 'minimal', they're fundamental.