this appears to be standard wording in their letters
What letters? You lost the PCN and so the only other correspondence you have is their NoR.
Anyway, what I quoted comes from here..
Duties of an enforcement authority to which representations are made under regulation 5
6.—(1) This regulation applies where an enforcement authority receives representations from a recipient under regulation 5.
(2) The enforcement authority may disregard any representations which it receives after the end of the period of 28 days beginning with the date on which the relevant enforcement notice is served.
(3) If the representations are—
(a)made in accordance with regulation 5(2), and
(b)not disregarded by the enforcement authority under paragraph (2),
the authority must, within the period of 56 days beginning with the date on which it receives the representations (“the 56-day period”), comply with the requirements specified in paragraph (4).
(4) The requirements mentioned in paragraph (3) are that enforcement authority must—
(a)consider the representations and any supporting evidence which the recipient provides, and
(b)serve on the recipient a notice of its decision (a “decision notice”) which states whether or not it accepts the representations made by the recipient.
(5) If the enforcement authority accepts the representations—
(a)it must cancel the relevant enforcement notice,
(b)its decision notice must state that the enforcement notice has been cancelled, and
(c)when it serves the decision notice, it must refund any sum paid in relation to the relevant enforcement notice.
(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—
I'm struggling to find anywhere where the time periods commence after service, but if you have any as regards the TMA General or Appeals regs, pl show.