From the online documentation in the Overview of MI procedure:   Multiple imputation does not attempt to estimate each missing value through simulated values. Instead, it draws a random sample of the missing values from its distribution. This process results in valid statistical inferences that properly reflect the uncertainty due to missing values—for example, confidence intervals with the correct probability coverage.   You may want to pick a larger number of imputations and then apply your filters from the generated data to restrict dry < wet mass. ... View more