The change of bound state energy spectrum interval for a fixed value of potential depth parameter versus ε + = 0 . When ε + = 0 , the energy spectrum is constituted with the values of energy between F to I points. While the ε + = 0 increases the Klein-Gordon energy interval shifts to be D to H. Note that the spectrum interval gains a symmetry when ε + takes the half value of the neutral Kaon mass energy.