You can modify this part and increase the divisor (which is currently set at 100)
getbattleflag("base_exp_rate")/100,getbattleflag("job_exp_rate")/100,60;
So it can be like this;
getbattleflag("base_exp_rate")/100000,getbattleflag("job_exp_rate")/100000,60;
Or until it doesn't overflow anymore.