I've never followed a diagram before but the pattern is in Icelandic so...here we are.
I Google Translated the pattern as mine was coming out very small. It said to repeat rounds 5 and 6 three times. As each round increases, repeating round 5 into round 6 makes a very odd, holey shape - do you think it's possible it meant three rounds of five and then three rounds of 6, or have I missed something obvious?
Also, where would you be inserting your stitch for the double crochet? I looked at other diagrams and they seemed more distinctly into a specific stitch and not through the middle.
Sorry if none of this makes any sense. I've never tried to articulate crocheting thoughts before.
In my experience the pattern you're posted (ie the diagram) is for the proper full pattern - it will just be the written out one which says 'repeat x'. What happens if you compare your version with the pattern version?