Since it's now "easy" to breed next to perfect IV Pokemon, people are always typing out the IV spread. Instead of that, why not create a notation, like we use '@' to denote the held item. Something like P-Atk (Perfect except for attack) so there's no need to write out (31,x,31,31,31,31), or P-SpA/Spd instead of (31,31,31,x,31,x). It's just easier to read and to write.