DEAR is coded from (7) (21) (21) (7)

NOSE is coded from

If u take place value of each letter then odd places are assigned 21  and even place values are assigned 7.....

as per this logic 7 21 21 21 can also be correct  

perhaps, 21 signifies the vowels, and 7 signifies consonants. makes sense?

Someone Plz give logic as to how it can be 7 21 7 21

7 21 7 21

(7)(21)(21)(21)

7 21 7 21

(7) (21) (7) (21)