Do NOT click the Remove Format button.  That will remove the ENTIRE Row Format.

Remember that a Row Format can be used in more than one statement.  To check that, go to General Ledger and click on the Design Statements super tab.  You should be viewing a list of the Statements.  If not, click on the binoculars button on the toolbar.  Read down the list of Row Formats and see where else this Row Format might be used.

If you want to remove the line from all the Statements that use that Row Format: 
1. Click one of the Statements and then click the Row Format tab.  
2.Select the line you wish to remove by clicking on it
3.Then click the  X on the toolbar to delete it.

If you only want to remove the line or row from ONE of the statements, then you will have to make a copy of the Row Format first by clicking on the Create/Copy Format button and then follow the above instructions to remove the line from that format.

You'll need to update the Statement record with the new copied Row Format.