Multiple payment term with different day limit

We have three payment terms with multiple day limit. for example: ED11 (day limit 10), ED11 (25 day limit) and ED11 (32 days).

User enter just ED11 but i dont understand how system understand which out of the three is the require payment term.

Users feel that due date calculated is wrong. In most case it calculate the due date exactly based on the days mentioned in the payment term. In all cases, days mentioned are 90 days.

In one case, due date if it is (just 90 days) 30/04 but user feels it should be 10th May in the following (obviously he is reffering to ED11 daylimit 10). In this case, SAP calculate 90 days. Is it because of too many payment terms which same name.

Best,

Bala