Particularly in the early laboratories, you'll find a last minute rush of students who have completed the work for the deadline just at the end. There are three obvious ways to handle this.
You could tell the students there is no time to mark it now, and they should get the extension instead. But this is a little discouraging for the students, and so is not as good as the next two methods.
If you believe the students really have finished, and there's normally no reason why you should not believe them if they say they have, you can record a tick in column 2 (i.e. saying ``yes they did meet the deadline''), and place a capital `D' in the mark column. This code means ``requires demonstrating'', which is the truth if you are intending to mark the work with the student in the following session. ARCADE, in its regular automatic email to the students will remind the students that this work needs marking. If the work ends up not being marked, despite ARCADE reminding the students, eventually the capital `D' can be changed to a lower case `d', which means ``missed the demonstration''.
If appropriate, you can also ask students to labmail the work (see § 9); they should reply that it has not been marked when prompted. When they actually later get the work marked, they can labmail the file(s) again, including a comment in each saying that it is now marked -- labmail will then archive both copies (it discards identical copies) and if necessary we can later ensure that the `finshed' work is the same as the `marked' work.
If you are concerned that the backlog of marking may start to build up, then the third approach is to ask the students to give you a print out of the work for off-line marking (labprint output is most useful here). Of course, not all laboratories are suitable for this, and it's not as ideal as marking with the student present. But it is better than getting a long way behind with the marking. (Exceptionally, some laboratories are normally marked off-line anyway.) When you do this, it is most important to tick the appropriate column to say the work has been completed (i.e. column 2 if it's completed by the deadline). If you do not tick this, then ARCADE will think the student has missed the deadline, and unless they have also got the extension, will automatically tell them that their work is now late! Leave the Mark column blank: this means the work is ``being marked'', which is the truth. You can distribute the listings to the demonstrators and pay them for the extra off-line hours they take marking the work.