If you're only seeing partial results from your Supermetrics queries in Google Sheets, it's likely that your query's row limit is too small for the full results to appear.
To fix this, open the Supermetrics sidebar, navigate to the Split by dropdown, and adjust the # of rows to fetch setting.
For some data sources with query types, the setting for the number of rows to fetch is under Report configuration, and called # of rows per item.