This usually happens because the folder is in OneDrive and Files On Demand is involved.
When a file or folder is only represented by a placeholder or link on the PC, Windows can show a difference between Size and Size on disk. In that case, the content counts toward the folder’s logical size, but little or none of it is actually stored locally, so Size on disk can appear as 0 bytes.
The screenshot shows the folder under C:\Users\lyman\OneDrive, which matches this behavior.