SPACI score report for 4at6 in ASTRAL 2.04:

PDB Entry: 4at6
SPACI score: 0.23
AEROSPACI score: 0.23

Experiment type: XRAY
Resolution: 2.55
R-factor: 0.2813
PCK1 PROCHECK Ramachandran: 1
PCK2 PROCHECK Chi-1 angle: 1
PCK3 PROCHECK H-bonds: 3
WCK1 WHAT_CHECK Packing: -1.772
WCK2 WHAT_CHECK Ramachandran: -3.863
WCK3 WHAT_CHECK Chi angles: -1.607
WCK4 WHAT_CHECK Backbone: 1.312

Note: Here are links to pages about PROCHECK and WHAT_CHECK.

Here is the full WHAT_CHECK report on this protein (linked from the WHAT_CHECK site).