My Daughter Had A Fluoroscopic Upper GI With KUB. Most

My daughter had a fluoroscopic upper GI with KUB. Most of the findings are normal, but I have been unable to figure out what the following sentence is stating, "There is under distention of the stomach with some prominence of gastric mucosal folds which may be due to the under distention."
Can someone please help me understand what this is stating? We don't see the GI again for 2 weeks.