On my screen, I have a different mouse pointer.
I have tested on several devices some of them were with retina display, some of them were standard (1920x1080). My guess was, that retina display and scaling might be the cause, but it was reproducible on other devices too.
I use the chart without any modification. I mean I do not maximize or minimize anything. I just mouse over on the red cursor.
On my pictures, I use Windows 10 Magnifier to show what is happening near the point.