According to new research by OpenUp, a behavioral research start-up based in New York, online shoppers have a good grasp of how much time they spent browsing for and purchasing items — but they have a far more tenuous grasp of how much money they spent.

The 1,000 subjects studied over two months in 2016 "severely underestimated what they actually purchased," writes Ashwini Anburajan, founder and CEO of OpenUp.