@acl when posting google street view links please post the short version as explained here (https://www.ftla.uk/civil-penalty-charge-notices-(councils-tfl-and-so-on)/read-this-first-before-posting-your-case!-this-section-is-for-council-tfl-dartme/).
The 14 day discount period expires at midnight on Tuesday, so I would recommend you make an informal representation explaining that you misunderstood the signs, here's a draft:
Dear London Borough of Richmond Upon Thames,
I'm afraid to say I misunderstood the signage at this location, at the time of parking I was labouring under the misapprehension that my B1 parking permit allowed me to park in this bay. I now understand that this is not the case and the regulatory sign for the bay takes precedence. I would hope that you would agree to waive the penalty for a local resident who made a genuine mistake on this occasion.
Yours faithfully,
Make sure to keep a screenshot of the confirmation page.