First, IC50 curves are not linear functions. They are saturating and take a hyperbolic form similar to that of the Michaelis-Menten equation.
Secondly, it is not clear what is represented by the axes. If the y-axis is % inhibition and the x-axis is inhibitor concentration (which would be normal for an IC50 curve), then you have a problem because there is 94.715% inhibition at zero inhibitor.
But you have a problem where the resuls be as negative values because there is 94.715% inhibition at zero inhibitor. So you should minimize the concentrations and reploted the curve.