Do you know what the target was based on? Some schools use CATs tests as they find them more reliable than KS2 levels. Or a combination of the two (sometimes with reading age added, or another measure.)
It may be that your child has made better than expected progress, I reckon the cure for that s a big well done hug! I also had a chat about how targets are made of tissue paper, and it's great fun to rip through them. When you're beneath them, you should be able to see the light through the tissue and it's important to know how to get to it... What steps can you put in place, what's needed for the higher level/sub level. Targets in the teachers marking, or the markscheme they give with a task should help you.
It's nice to see they're doing so well