chapter 17 GridBarChart, inconsistency in frame fading when screen orientation changes

[mhDuke]

when tapping a bar(boxView)in the chart, the event OnBoxViewTapped runs to set overlay(Frame).Opacity = 1. the timer below then fades that frame out. the issue is when screen orientation = Landscape it takes much more time to fade than in Portrait orientation!

Device.StartTimer(TimeSpan.FromMilliseconds(15) , () =>
            {
                overlay.Opacity = Math.Max(0, overlay.Opacity - 0.007);
                if (overlay.Opacity == 0)
                    overlay.IsVisible = false;
                else overlay.IsVisible = true;
                return true;
            });

couldnt find a solution or reason for this inconsistency!