Doubt about "effect size": standardized mean difference

Hi everybody.
I have a question about how to interprete a standardized mean difference.
I was reading a meta-analysis in which the authors calculate the SMD, because they evaluate continuos variables (a linear measure in mm), of the same outcome, assessed in different ways.
The reported SMD is 0.61.
Than they state "Finally the dimensionless value of SMD obtained from the random effects model was multiplied by the standard deviation to find the actual difference in the variable"
The value resulting from this calculation is 1.81 mm, which is higher than all the single value reported in the individual studies before data being pooled.
Is it possible or is there a mistake in the last calculation?

Thank you.