How to indicate the merged volumes in OJS 3

Hi all!
I wonder how to indicate merged volumes in OJS 3. We had published some issues in 2000’s that were merged (e.g. vol. 15 and 16 were published at once in a single journal issue). Now when I try to create a new issue in OJS with “15-16” in field “Volume” it is cutting the string and I obtain “15” only.
Thanks for ideas and help!