Can anyone make my Chinese-English translation sound better? I need to translate this passage in traditional Chinese into English:

教學年資：在本校升等時職級滿三年為50分，每增授課一學期加1分，最高分為70分。

Here is my own translation (Please bear in mind that I am still learning to how to translate):

Years of teaching: To apply for promotion, the teaching staff needs to have fulfilled 3 years of service to obtain 50 credits with one additional credit for every course taught over 1 semester. The maximum of credits shall not exceed 70. 

Any thoughts?
在本校升等時，職級滿三年為50分，每增授課一學期加1分，最高分為70分
When applying for promotion at the University, those who have held their current rank for three years will receive 50 points, with an additional point for each semester of teaching beyond [the three years], up to a maximum of 70 points.

The word 申請 'apply for' is omitted at the beginning (在本校申請升等時) and there should be a comma after that. The word 'rank' 職級 is used oddly, I think 以原職級任教滿三年 or 服務滿三年 would make more sense. The intent is probably that one must hold each rank for a minimum of 3 years before applying for promotion (assistant to associate, associate to full), but this wording doesn't really make that clear. 每增 is also not very smooth.

The main problem with the translation is that 'credit' is not right here, this is a point system; also for every course taught over 1 semester is not right, the intent of the Chinese text is clearly to count semesters of teaching, not courses taught