Skills can be listed with or without an associated level. If no rank is listed, then you gain that skill at level 1 if you do not have it already, or increases its level by +1 if you are already trained in that field. If a rank is listed, then you gain the skill at that level so long as it is higher than your current level in that skill.
For example, Gambler 0 would mean you receive the Gambler skill at level 0. This is of benefit to you only if you have no Gambler skill.
Vacc Suit would mean you increase your Vacc Suit skill by +1, or gain it at level 1 if you have no Vacc Suit skill to begin with. If you have Vacc Suit 0, it increases to 1, if you have Vacc Suit 2 it rises to 3, and so on.
Streetwise 1 would mean you get the Streetwise skill at level 1. If your Streetwise skill is already 1 or more, then this is of no benefit to you. If you have no Streetwise skill, or it is only at 0, you jump straight to Streetwise 1.