January 7110 february 826 march 5313 april 541 may 3513 june 4610 july 4710 august 681 decipher the logic and find out the number for september

First, we make some observation:
January - Has 7 letters,is the 1st month of the Year, and J is the 10th letter in the Alphabet=7110
 February -  Has 8 letters,is the 2nd month of the Year, and F is the 6th letter in the Alphabet= 826
March -  Has 5 letters,is the 3rd month of the Year, and M is the 13th letter in the Alphabet=5313
April -  Has 5 letters,is the 4th month of the Year, and A is the 1st letter in the Alphabet=541
May -  Has 3 letters,is the 5th month of the Year, and M is the 13th letter in the Alphabet=3513
June -  Has 4 letters,is the 6th month of the Year, and J is the 10th letter in the Alphabet= 4610
July -  Has 4 letters,is the 7th month of the Year, and J is the 10th letter in the Alphabet=4710
August -  Has 6 letters,is the 8th month of the Year, and A is the 1st letter in the Alphabet= 681
 September -  Has 9 letters,is the 9th month of the Year, and S is the 19th letter in the Alphabet= 9919

September 9919