Imported products are distinguished by Item Number. If the Item Number already exists, then its corresponding product will be updated. Import requires a lot of memory resources. That's why it's not recommended to import more than 500 records at once. If you have more records, it's better to split them to multiple Excel files and import separately.
Lorem ipsum auctor eros nibh laoreet proin congue torquent leo ligula, integer orci magna consectetur nibh et pellentesque nisl potenti luctus, id class lorem nostra quis integer quisque taciti interdum.
Ornare mattis vitae litora scelerisque enim eleifend, tempus sem massa risus enim, sociosqu etiam sagittis id fames quisque sagittis diam at iaculis proin lobortis ornare porttitor semper lacus ultrices mi.