The figure below shows the Sending section of the Preferences dialog:
In this section you configure the default paramenters used when sending several commands at once. This setting is used in the Command History (Section 6.3.4, “Command History”) and Multi-line Send (Section 6.3.5, “Multi-line Send”) dialogs.
You specify the number of commands or lines that are sent simultaneously, and the delay between sending each group of commands/lines (containing the specified number of commands/lines, naturally). Note, however, that the values you set here are only defaults, you can change the values in the dialogs of those features if you need so.