With these two concepts, limitation and expansion, the numbered cards of the deck can be seen as acting in accordance with this, either to expand or limit the energy of a given card. And this, in turn, can indicate a positive or negative dignity- remember that for these purposes a positive dignity is one that acts favorably (expands or intensifies the energy of a given card) towards the situation, and a negative dignity is one that acts antagonistically (reduces or limits the energy of a given card).
Notice also that both the Aces and 10s are considered neutral in this system- this is because both represent potential. What we use this potential for can be either good or bad; think of them as raw material, that can be used to make a weapon to harm or a tool to construct. We find the following numbers with their respective categories:
Positive: (Expansive, increasing and supporting) 2, 4, 7
Negative: (Limiting, decreasing and setting boundaries) 3, 5, 8
Neutral: (Representing potential and raw material) Ace, 6, 9, 10
Considering also the elements, there are two ways to look at the cards- one is to consider their elemental assignment or placement in terms of the Zodiac, which is useful in terms of the Major Arcana, as well as their numerical value, which is useful for the Minor Arcana. However, the elemental assignments of the Minors can also be taken into consideration, as each of the four elements represents an area of our lives, relationships and development. In terms of dignities, this can likewise indicate a little more about that particular dignity- here the elements can indicate what area that positive influence is coming from. The Swords indicate communication, thought or ideas. Cups indicate spiritual, emotional or relationship factors, Wands indicate will and determination, and finally Pentacles indicate material resources. This is a somewhat arbitrary system, and there is bound to be a good deal of overlap, so again, use your own judgement on what each dignity can mean, and be sure to take the situation into account as well.