If you do the learning on your own try to observe yourself and don't just follow what s repeated over and over. I would politely challenge 25/10 as a beginner's speed, and would challenge any set speed limit for training. I change my speeds all the time, depending on my form of the day.
Starting with a reasonable speed of 10/10 and then work your way up is what worked for me. That was before there was any discussions on dit counting and long before Internet as way know it ...
I think the 25/10 is aimed to stop speed merchants wasting their time learning at an unnecessary slow speed ( for them ).
Some people report getting to 25/25 in a few weeks.
The rest of us may well end to getting to lesson 40 at 10/2 in the end, after a long struggle.
If Mark ensures that he is making real progress then 25/xx will be OK - for him anyway, but only he can tell . . .
G4FON recommends starting at the speed you are aiming for eg. 25/25
see https://youtu.be/jBmuoLUV1LM 7:13 ... and 9:24 9:50