Boolean Recommender evaluator returning score greater than 1

[Steven Bourke]

Hi, 

I've removed all preference values from a dataset and plugged it into a  
boolean recommendation configuration. When I run RMSRecommenderEvaluator on the 
dataset I get values back which are higher than 1 (But lower than 2). I assumed 
that the highest value that should come back from the evaluator is a one. If my 
reasoning is correct, can anyone recommend what could be throwing the incorrect 
results?

Thanks