R , repeat is the key ;-)
But if I can copy at 25 , then can I too copy at 15-20 ?
Probably - the issue whereby people who can ( and therefore always do ) copy at high speeds like 35 - 40 wpm and above report having difficulties at 5 - 10 wpm . .
. . . is probably due largely to these faster copiers hearing the whole word as a single entity
- rather like we do visually when reading text
. . . but then having to collate letters at 5 wpm and then spell out the word is more of a challenge for them ( me too ) and less of a practised skill.
For learning - I think you are best advised to set the character wpm as high as is comfortable
- fast enough to hear a character single entity rather than a collection of dah-dits
and then adjust the "effective speed" downwards until you can decode quite long strings of characters without falling behind.
I also advise testing a few different audio frequencies, because my hearing response to code isn't anywhere near flat right across the audio range.
I am unlikely to be unique in this regard.
If you are decoding along quite easily without counting then you will speed up over time as a matter of course just through practise.