The stat-values (not the stat-levels) of the offspring are calculated like for a creature that was just tamed with a 100% taming effectiveness with the taming effectiveness bonusses applied. This means that an offspring can have higher values as its parents in stats that gets a bonus depending on the taming effectiveness (for most creatures this is Melee Damage and sometimes Food). See also Creature Stats Calculation for how the values are calculated from the stats.