使用2位数和单位数编制最大值

I'm currently developing a code which works out the highest score out of the score it has on the csv file. For example if the score is 10 and 4 , the highest score should be 4. However it does not work if the number is 10. It works fine if the number is 5 and 7 or any 1 digit number. I'm currently developing a code which works out