Dashboard subscribers statistics issue

When I (on the dashboard) hover with the mouse over the individual data points in the subscribers graph, I (should) see a small black box with the number of subscribers of the selected month.

The issue is that the black box is too small to contain all text. And because the font color is white and the background of the graph is white/grey, the text is hardly visible. This happens with the Brave browser with "Shields up", not with Firefox.