Restrictions work by using the lowest value to calculate the loan period. If you have created some new restrictions and your loans are not behaving as you expect, it is likely there is another restriction affecting it too.
For example, if your borrowers are set to 21 days but the resource restrictions are set to 14 days the resource will be issued for 14 days as per the lowest value. Altering the lower number to match the higher one, or turning it off all together, will correct it and allow resources to be issued for 21 days.
Another issue could be if you have set a resource specific restriction on a borrower restriction with different loan periods, again it will always take the lowest.
The only situation where this would not take place, is where a loan period has been set on an individual resource. The value set for the individual resource will take precedence over any other restriction, regardless of whether it is a higher or lower value.