The balanced equation of potassium permanganate and oxalic acid  reaction in acidic medium is shown below.

$2\mathrm{K}\stackrel{+7}{\mathrm{Mn}}{\mathrm{O}}_4+5{\mathrm{H}}_2\stackrel{+3}{{\mathrm{C}}_2}{\mathrm{O}}_4+3{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{dil}.\right)\to {\mathrm{K}}_2{\mathrm{SO}}_4+2\stackrel{+2}{\mathrm{M}}{\mathrm{nSO}}_4+10\stackrel{+4}{\mathrm{C}}{\mathrm{O}}_2+8{\mathrm{H}}_2\mathrm{O}$

The initial oxidation state of carbon in the oxalic acid is $+3$. The oxidation state of carbon at the end point is $+4$(in carbon dioxide). Hence, the change in oxidation state of carbon at the end point is 1.