I had white stool mixed with brown stool in the same bowel movement. what does that mean?

Clay colored or white stool denotes a lack of bile which occurs in gall bladder,bile duct obstructions,liver and pancreatic pathology. You may have had some transient cause if your stool has fully returned to normal brown color and not persistent clay colored,or very pale loose stools. A gastroenterologist would be best to evaluate and advise you. Appropriate testing will be done