Is it appropriate to run correlation on continuous y value with discrete x value?
Your feature "Distance from the edge" is represented as a factor (), which means it is interpreted as a categorical variable. You need to make sure that it is interpreted as a numerical (either integer or double) and this should label it appropriately in your plot and also correctly display the distance between them (as they are not evenly spaced).
This might help to get the type right.

Check this answer for a discussion on what correlation methods to use for continuous and discrete variables.