When a unit containing Stubborn loses a Round of Combat, the modifier to the Courage from the Combat Score difference is halved, rounding fractions up (i.e. towards a larger modifier). Note that if the unit is also Steady, the modifier is first set to no smaller than 2 following the Steady rules, and then halved, rounding up, to 1.
If the unit is Unstable, the Health Point losses due to Unstable are halved, rounding fractions up (i.e. towards more Health Point losses).