Below is the relevant part of the traffic order which suggests that the contravention description may be correct if say physical visitor permits are available.
OP - if you can check signage at start of Mildmay Road that would be useful.
Also one relevant appeal that suggest Redbridge doesn't know what it's doing.

Case reference 2240350574
Appellant No Word LTD
Authority London Borough of Redbridge
VRM BL07BFN
PCN Details
PCN AF07248425
Contravention date 26 Mar 2024
Contravention time 15:26:00
Contravention location Mildmay Road
Penalty amount GBP 130.00
Contravention Parked in permit space without a valid permit
Referral date -
Decision Date 18 Oct 2024
Adjudicator Anju Kaler
Appeal decision Appeal allowed
Direction
cancel the Penalty Charge Notice.
Reasons
The agreed facts are that the vehicle was at the stated location as shown in the Civil Enforcement Officer’s photographs and a Penalty Charge Notice was issued. The Authority asserts the location is within a Controlled Parking Zone.
A single yellow line denotes that restrictions apply at certain times during the day. The Authority has uploaded black and white photographs. There are no single yellow lines seen where the vehicle parked. The Zone Entry signs have no meaning here. I allow the appeal.