I believe that we may have addressed this query via email correspondence already, but for the benefit of future readers I have provided the answer below.
The Annotations that we use in our library are restricted to the plot area only which means that they will be clipped when near an axis. With this in mind we need to use alternative methods to achieve the desired result.
It's possible to place a regular view on top of your chart and then position it appropriately. In order to know which pixel values to use when positioning this view we have provided a useful method on the Axis called getPixelValueForUserValue(T userValue). This allows you to provide a data value which will be translated to a float representing the pixel value for that position on the axis. It's important to note that this pixel value is relative to the starting edge of your ChartView.
One other piece of information to keep in mind when attempting this approach is that this method will only return meaingful information after the chart has been laid out. For this reason we provide a OnInternalLayoutListener callback which is called after the chart has finished laying itself out. You will need to make sure that you are calling getPixelValueForUserValue after that callback has been called rather than just in your OnCreate.
You will be able to find all this information in our docs: http://www.shinobicontrols.com/docs/ShinobiControls/ShinobiChartsAndroid/1.7.1/Premium/Normal/apidocs/docs/reference/com/shinobicontrols/charts/Axis.html#getPixelValueForUserValue(T) I hope this has been helpful and let us know if you have any other questions.