Animtim will certainly have a better view than mine but for me it was not a problem as the blackboard is more there as background.
I find it better if when possible the score is as big as possible as GCompris is also played on very small screens like phone screens.
It is true that the overlapping was not really a problem. But since your change doesn't have any bad side effect I'm ok to get it merged.
Also I'll refactor the graphics and layout of this activity at some point later anyway, so this little patch is good for now.
committed in https://commits.kde.org/gcompris/e185c82d21879412ef448ab838655699fb340937 with some changes
hardcoding a value is never good when you have the possibility to use anchors.