This genotype technically represents carrying two copies of the D409H mutation in the GBA gene, and thus most likely a form of Gaucher's disease. However, errors in interpretation for C/G transversion mutatations occur far more frequently than Gaucher's disease does, so this is likely to actually be an error.
Why is this? Interpretation can be problematic due to orientation issues involving ambiguous flips. To make matters even more confusing, in the past, dbSNP (erroneously) defined the minus strand 'ancestral' (i.e. normal) allele as C, although it currently (correctly) defines the minus strand ancestral allele as G. In SNPedia, the orientation is set to the plus strand, which means the normal allele (for the plus strand) is C. This is also the orientation currently used by 23andMe.