The selection component lets you select which rows in the source sheet will be processed.
TIP: if you are not sure which rows will be processed click the eye icon. Add-on displays the start row and how many rows will be processed for the option you selected.
Add-on processes all data rows in the source sheet starting on row 2.
From Last Processed Row
Add-on continues from the last successfully processed row number. This option is handy when you keep adding data and you lost track which row was processed as the last one. Also, data might come from various channels like Google forms and when you re-open the add-on you might not know which row was processed as the last one. Use this option to continue from last position.
Add-on processes only selected rows. Hold the Ctrl button and click on row numbers in the source sheet to select one or more rows. Or hold the Shift button and select a range of rows you want to process. This option is super-handy for reprocessing when you made some adjustments in data and you would like to pick only one or few rows to be reprocessed.
From Selected Row
Add-on processes all rows from the selected row down (including the selected row). Hold the Ctrl button and select exactly one row.
Show Start Row
Add-on displays the start row number and how many rows will be processed. Add-on guides you in the selection process and might return some warnings when you make an invalid selection like incorrectly selected rows. Once the add-on stops complaining you are ready to go.