checkCIF procedure

PLAT733

 A large ratio of the reported and calculated torsion angle s.u.'s is found.
 This check should warn for erroneous rounding: E.g. 105.5(19) to 105.5(2)  
 or 105.0(5) to 105(5) etc. 
 Note_1: s.u.'s on the unit-cell dimensions are taken into account in the   
 calculation of expected s.u.'s. This may result in large differences between
 expected and reported s.u.'s when this contribution is not included in the
 reported s.u.'s, in particular for inaccurate unit-cells.   
 Note_2: Another source for the discrepancy between calculated and reported
 s.u.'s can be that the validation software has access only to the variances
 of the refined parameters as opposed to the full co-variance matrix used by
 e.g. SHELXL for the calculation of derived parameters with associated s.u.'s.
 Constrained/restrained refinement may cause large co-variances.