I'm not familiar with the total_committed field. Do you know what ONTAPI call(s) that OnCommand API Services is making to ONTAP to get that information? I tried looking through the ONTAPI to REST mapping document to search for the total-commited property in an existing ONTAPI, but I didn't find it there: https://library.netapp.com/ecm/ecm_download_file/ECMLP2879870
I'm wondering if it is some calculation that OnCommand API Services is doing. If so, you might want to reach out to support for that product and ask how you can get that same value via ONTAP.