Hi u can change it here
https://github.com/rathena/rathena/blob/master/src/map/pc.c#L6338
if(sd->state.showexp) { char output[256]; sprintf(output, "Experience Gained Base:%u (%.2f%%) Job:%u (%.2f%%)",base_exp,nextbp*(float)100,job_exp,nextjp*(float)100); clif_disp_onlyself(sd,output,strlen(output)); }