Also, you need to take a look at how defensive structures handle their bonuses. For example, K_Fortress (kingdom fortress) is supposed to add 25% defense to units defending the city with this xml
<GameModifier>
<ModType>City</ModType>
<Attribute>AdjustDefendingUnit</Attribute>
<Value>125</Value>
<Provides>+25% Unit Defense</Provides>
<Operator>%</Operator>
<StrVal>UnitStat_Defense</StrVal>
<PerTurn>1</PerTurn>
</GameModifier>
However, it adds 125% (a total of 225%) instead of the intended 25%. The cause is mis-use of the <Value>. This bug is in all defensive structures.