After the training-and-prediction phase, each experimental retention time was complemented by 5 additional predicted values. Then the absolute and relative differences between the experimental value and the predicted ones were calculated. For each model, entries that fell within the worst 5% for both absolute and relative differences simultaneously were flagged with a "yellow card", so that each entry received from 0 to 5 "yellow cards". We can speculate that entries with 0 "yellow cards" are likely normal, while entries with 5 "yellow cards" are extreme outliers. They are either too unique for meaningful predictions or contain incorrect experimental values in the database.