To assess the performance of the CNL model, TP and TN fragment cases were obtained from databases. For this, the 81,417 measured spectra from MassBank EU and MoNA were used ( ). The TPs here were the CNLs generated from the true experimentally assessed fragments of a chemical. As for the TN CNLs, for each spectrum, 200 random masses (i.e., between 50 Da and precursor m/z) were generated and checked against all spectra of the compound in question to ensure that no m/z value of the random TN fragments were actually a true fragment of that compound. Then, the randomly generated m/z values were converted to TN CNL values. Overall, a total of 2,286,269 TP CNLs and 3,994,694 TN CNLs were obtained via the above mentioned approach.