If a report includes a lookup field pointing to a Quote, and that Quote has since been deleted, the report shows a dash ('-') in place of the Quote's name, rather than leaving the cell entirely blank or throwing an error.
The report row itself, and the record it belongs to, still exist. What no longer exists is the specific Quote that was being referenced. Rather than the report failing to render that row, or silently dropping the reference, Zoho CRM shows a dash as a placeholder to make clear that a value was once there but the linked record is now gone.
If you're seeing more dashes than expected in a report, it's worth checking whether Quotes (or whichever related record type is showing the dash) have genuinely been deleted, whether intentionally as part of a clean-up, or accidentally. Deleted records typically sit in the Recycle Bin for a period before being permanently removed, so a recently deleted Quote can often still be restored if the dash wasn't expected.