When you choose Go To in the Find menu, or press Command-L, CotEditor displays the Go To dialog box to give you quick access to the character(s) or the line(s) you want to see.
In the dialog box, choose either Character or Line, enter the character/line number, and click Select.
If you choose Line and type in “3”:
=> The line 3 (the third line from the top) will be selected.
If you choose Line and type in “3:2”:
=> What this indicates is “starting from line 3, select 2 lines.” Thus, the line 3 and 4 will be selected.
If you choose Line and type in “3:-1”:
=> What this indicates is “starting from line 3, select the rest lines except the last 1 line.” Thus, if the document has 10 lines, the lines from the line 3 to 9 will be selected.