This is normal. The meaning of the "10/10A" is that the chargepoint is offering 10A (2nd figure), and out of that the car is currently using 10A (1st figure) - in this case, all of it!
So the 10A is set by the chargepoint, in this case your UMC cable. The UMC in turn decides how much to offer the car depending on which type of plug adapter you have connected, and for the UK 13A plug that is 10A. If you used the blue 16A commando adapter, it would offer the full 16A rating of that plug.
The reason for the lower figure for 13A plugs is a compromise: although originally designed back in the 1940's to deliver 13A, experience has shown that modern 13A plugs/sockets are not robust enough to reliably deliver 13A for hours on end, as they will be used for EV charging.
You will find that just about the only appliance currently sold that takes the full 13A from a 13A plug is a kettle - which of course only runs for a few minutes at a time. If you say "what about my 3-bar electric fire?", I challenge you to find an old-school 3-bar electric fire these days: most commonly sold are 2300W (ie, 10A), and in any case heating appliances are normally only used continuously when it's very cold and so overheating risks are lower.
Even the 10A isn't low enough to guarantee no problems with the overheating of plug/socket contacts if you happen to encounter and old and worn (or new and badly made) socket, but it's usually OK. Note that heating effects are proportional to the square of the current, so although this is only a 23% reduction in current/power compared to 13A, the heating effect is reduced by 40%.