8 And these are the names of the children of Israel, which came into Egypt, Jacob and his sons: Reuben, Jacob's firstborn.
9 And the sons of Reuben; Hanoch, and Phallu, and Hezron, and Carmi.
10 And the sons of Simeon; Jemuel, and Jamin, and Ohad, and Jachin, and Zohar, and Shaul the son of a Canaanitish woman.
11 And the sons of Levi; Gershon, Kohath, and Merari.
12 And the sons of Judah; Er, and Onan, and Shelah, and Pharez, and Zerah: but Er and Onan died in the land of Canaan. And the sons of Pharez were Hezron and Hamul
13 And the sons of Issachar; Tola, and Phuvah, and Job, and Shimron.
14 And the sons of Zebulun; Sered, and Elon, and Jahleel.
15 These be the sons of Leah, which she bare unto Jacob in Padanaram, with his daughter Dinah: all the souls of his sons and his daughters were thirty and three.

An artificial problem. Simple maths will get the job done:
1)Reuben; Hanoch, and Phallu, and Hezron, and Carmi = 5
2)Simeon; Jemuel, and Jamin, and Ohad, and Jachin, and Zohar, and Shaul = 7
3)Levi; Gershon, Kohath, and Merari = 4
4)Judah; Er, and Onan, and Shelah, and Pharez, and Zerah, Hezron and Hamul = 8
5)Issachar; Tola, and Phuvah, and Job, and Shimron = 5
6)Zebulun; Sered, and Elon, and Jahleel = 4
TOTAL = 33
The text doesn`t say all of Leah`s children came down to Egipt, it only reckons the ones she bare to Jacob. Dinah was not Leah`s daughter