i have never read a more unclear letter, anyone who understood what it said?

also, how is 7% more than 24%? i mean in terms of stat increase that the new mount update did, i did it 5 times all got less.

It means that some of the values shown for level up stat growth spans were rounded, which lead to lower than expected growth in some cases. The mount growth reset item got sent if you had trained a mount during that time (aka directly after the maintenance of Jan 23rd until Jan 24th when the mails got sent).