When we get our CATs tests marked, we get a printed page per child. It tells us how many questions in each little test the child attempted and how many they got right. (So can give an indication on low scoring papers as to whether the child plodded and didn't answer many, or perhaps wizzed through rushing it).
It gives a standardised score for each battery of tests. As with all standardised scores, 100 would be the average score for a child achieving what they are supposed to achieve for their age. Above 100 is therefore good.
There are 3 bar graphs, one for each test (verbal, number, non-verbal) that give a percentage likelihood of the level that the child will achive. This is where schools can use them to target pupils. A pupil that has a high likelihood of achieving a level 4, but some possibility of getting a L5 can be targeted to try and boost them to a level 5.
They don't show any indication of level 6s at Primary level.
They are a prediction of what your child could achieve if they carry on as they are. I.E. no value added improvement. Therefore your child, if the school and they put in the required effort, should definitely achieve the predicted grade, and perhaps improve on that too. E.g. my daughter was predicted 3 5s and eventually came out with 2 level 5s and a 6 in maths.
We send home the results paper as a matter of course and have an open evening in conjunction with a parents evening to dicuss them with any parents. This works well.
Beware however, many schools (my child's included) don't send home or communicate the scores with the parents at all. I had to make a particular appointment to go in to view the results paper in the school itself.