Fighter pilots face the same issue...
Each nation has a different standard for verifying a kill. What may be a "confirmed" for one nation becomes a "probable" for another. Thus, scorecards, if I may use the term, must be approached cautiously and with a jaundiced eye. Additionally, as she became famous during Stalin's Soviet Union, there is a real possibility that there was some inflation of numbers for propaganda purposes. After all, morale had to be kept up at home and fear instilled in the "Hitlerites."