Highfield may have A cabinet directly outside but without a number we don't know which it is. There is something distinctly odd going on. I wonder if you were previously connected to another cabinet (probably cab3 in Finningham) and the checker has been updated with the new cab number but not the new projected speeds.
Not sure where to go with this.
I'll ask the mods if they can shed any light.
The other possibility is that because cab13 is a new cabinet, the network re-arrangement required to connect you to it hasn't been completed yet and you are seeing the result of still being connected to the old cabinet. Just a different variation of my previous post.
Welcome to the Community and thanks for your post!
Sorry about the confusion with the checker results. Strange issue! You can use this form to contact Openreach directly: Fibre Broadband availability
There is a drop down on their form for "Which cabinet am I connected to?" so all being well, they'll shed some light on this.
Feel free to post back and let us know how this goes!