Biopython: resseq doesn't match pdb file
Let's check it. I copied your file fragment into a.pdb.

&gt;&gt;&gt; from Bio import PDB
&gt;&gt;&gt; for res in PDB.PDBParser().get_structure('pdb', 'a.pdb')[0].get_residues():
...   print(res.get_full_id())
... 
('pdb', 0, 'A', (' ', 22, ' '))
('pdb', 0, 'A', (' ', 23, ' '))


So BioPython (ver. 1.66) gives 22 and 23 as expected.