I keep getting an addition of 2 extra hydrogens (2 amu) to the molecular weight of some structures converted from SMILES strings. This seems to happen only for a subset of structures that are somewhat more complicated. I have Chemoffice 19 plug-in for Excel 365 ( windows 10). When I use ChemDraw or our internal tools the problematic structures are converted to formula and Mw correctly. I only see the error in Excel.
Leo