While creating loan product, Enable 'Place guarantee funds on Hold'.
There you will see three fileds:
a) Mandatory Guarantee
b) Minimum Guarantee from Own Funds
c) Minimum Guarantee from Guarantor funds.
a should be equal to b+c.
If a=b then 'c' can be blank.
If a=c then 'b' can be blank.
If not, the loan product should not allow to be created and should throw proper error: "Mandatory Guarantee should be equal to sum of own fund and guarantor fund OR any one of them".