Exam writing box

Did you write outside the given lines and on the rest of the page?
Or did you write outside the borders on the edge of the page?
Because the first one is fine but the second one is not. I'm a GCSE student so take this with a pinch of salt but I'm pretty sure than when your papers are marked, they go through a scanner, and when the paper goes through the scanner, the parts outside the border get sliced off so your paper can be scanned and the pages in the booklet separated. So anything you write outside those borders on the page is sliced off and gone. If you only wrote outside the lines, and in the borders, your work will be read because the examiner when they see the scan of the lines can opt to see the whole page scan so they can see the work if it clearly didn't end on the lines.
I really really hope for your sake that you didn't write outside the borders and it is the first one. I guess if you get lucky, the person who feeds your paper in the scanner might notice before the borders get sliced off? But I wouldn't count on it.
Next time, I would recommend using all the additional pages and the end of the booklet, and if you fill those, asking an invigilator for more paper.