Since there are no lamp lumens with absolute photometry, all SSL's (LED's) are considered 100% efficient (Efficiency = Luminaire Lumens / Lamp Lumens). Efficiency is used as the baseline in a CU table. Baseline is an infinitely large room (RCR = 0) with zero reflectance (see image). From the baseline, reflectance is added to the calculations resulting in some of the lumens getting counting more than once. This results in CU values > 100%. In reality this cannot happen!
Bottom line - CU calculations were not designed with absolute photometry in mind!