The governing legislation in this case is the London Local Authorities and Transport for London Act 2003 which provides as far as is relevant that:
[a Notice of Rejection]
must—
(a)state that a charge certificate may be served under paragraph 5 below unless before the end of the period of 28 days beginning with the date of service of the notice of rejection—
(i)the penalty charge is paid; or
(ii)the person on whom the notice is served appeals to a traffic adjudicator against the penalty charge; and
(b)describe in general terms the form and manner in which such an appeal must be made,
and
1)Where an enforcing authority serve a notice of rejection, the person who made the representations under paragraph 1 above in respect of which that notice was served may, before—
(a)the end of the period of 28 days beginning with the date of service of that notice; or
(b)such longer period as a traffic adjudicator may allow,
appeal to a traffic adjudicator against the decision of the enforcing authority.
The NOR in this case refers to these timed periods as follows:
..pay within 28 days of the date of service of this letter;
.you may now appeal within 28 days of the date of service of this letter;
If you do not pay or appeal withi 28 days of the date of this letter then ..
..we may serve a Charge Certificate.
'Within' in this contect means from the date of.
With respect, every reference to 28 days in the NOR is incorrect.