The Molecular Weight and formula for the structure I have drawn does no match the known molecular weight and formula. It appears that an extra Hydrogen(s) has been added to the structure, but it is not clear where.
If you find that the formula and molecular weight are off by a Hydrogen(s), it is possible that you have a contracted label, such that the Hydrogens are there but not visibile. Select the structure with the lasso tool. Use the Expand Label command (see your manual for the location of this command for your version of ChemDraw). You may notice that the structure changes. This should help you figure out which label has expanded. Once you detemine this, use the Undo command to go back to the contracted state of the structure, then delete the label, and add it back.
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