Proficiency bonus

The proficiency bonus represents your dog’s growth in knowledge and experience. If your dog is skilled in something, you can add her proficiency bonus to appropriate die rolls. As she gains levels, your dog’s proficiency bonus increases over time. A first-level dog starts with a proficiency bonus of +2, and it’s applied in the following rolls:
 * Attack rolls using weapons for which she has an appropriate Aptitude trick.
 * Attack rolls with spells she casts
 * Ability checks using skills she has (see below)
 * Saving throws, based on her calling’s primary abilities
 * Saving throw difficulties for spells she casts

Your dog’s proficiency bonus can’t be added more than once to a single die roll or to another number. However, the proficiency bonus might occasionally be modified (doubled or halved, for example) before you apply it.

Primary Abilities
Each calling has two of the abilities marked as primary abilities. These two abilities are the ones the calling uses the most, particularly as part of their calling tricks. They also allow the dog to use her proficiency bonus for saving throws.

Advancement
Every two levels, the character’s proficiency bonus also increases by one.