What it teaches
Sums and differences inside twenty, in both directions — 8 + 5 and 13 − 5 are the same fact seen from two sides, and the game asks for both. This is the range the Polish podstawa programowa sets for klasa I, and the range an English Year 1 classroom calls "number bonds within 20".
The aim is recall, not counting. A child who counts on their fingers to 13 is doing arithmetic correctly and slowly; the point of practice is that the answer eventually arrives without the counting.
What to look for
Watch for the crossing of ten. Most children are steady on 5 + 3 and slow on 8 + 5, because the second one crosses a ten and the first does not. If that is where the pauses are, the ten frame in the second hint is the picture to talk about.
When the answers come back quickly and without counting, move to Adding and taking away to 100. There is no hurry: this range is worth a whole year.