How to sum the value of a specific cell

Hi @xiaoyu,

This is typically the sort of operation that OpenRefine is not designed for: I would do this with spreadsheet software like LibreOffice Calc or Excel instead.
There are convoluted ways to do this in OpenRefine (for instance by abusing the records mode) but it is pretty inconvenient and this is a sign that you trying to use the wrong tool for the job.

If you are sure you want to use OpenRefine for something like this I encourage you to check out this video series where you will see many tricks to do pretty arbitrary things inside OR itself: