According to Wikipedia, the Danish forces suffered 16 KIA, 14 WIA, and the Germans 203 casualties (killed and wounded counted together).
The source cited in the article for the German figure is a pair of books by E R Hooton; Luftwaffe at War in two parts, from 2007.
I understand that there was relatively little fighting during the Danish invasion - there was some token resistance along the border but the government soon ordered a surrender realising they had no chance of holding the Germans back.
So, assuming the figure of 203 Germans killed and wounded is correct, why the big imbalance? Did the Danes resist more fiercely than we thought? Was there a big traffic accident or ship sinking or something that counts for the figures but isn't attributable to Danish action directly? Or were the Germans just recording every bruised knee and sprained wrist as an "injury" which inflates the figures?
Mostly because the Germans were on the offensive. Throughout history, the offensive is mostly the side with most causalties. But, High number of deaths does not equal loss of battle. Also, keep in mind that the fighting in Denmark only lasted about six or so hours. It was the shortest campaign by the Germans. Not to be disrespectful to the Danes, but they didn't fight much. They held their ground for a few hours and then began to be pushed back and retreated. Soon after came the official declaration of surrender by Denmark.