Synology DSM Integration reporting different numbers to DSM itself

I’ve got a discrepancy between what DSM 7.2 reports in Storage Manager and what the Syno integrations is reporting.

Storage Manager reports 17.2TB used whereas the Syno integration is reporting 18.90TB (see screenshots below)

It started happening sometime in May, either with an HA update or perhaps a DSM Update - I can’t put my finger on exactly what because I didn’t notice it until recently.

Any ideas?