Base Attack Bonus and Base Saves

[ParadoxGamesHLM]

So, over the summer, the DM said we would be starting a new group of characters which adhered more strictly to the rules. However, I've had two lingering questions about base saves since I started playing.
Firstly, at each new level the base attack bonus and saves for a class are listed as +1, +2, etc. Does this mean that the current value of that base save is increased by that number, or increased to that number.
Secondly, after a certain level is achieved base attack bonus is shown with two numbers separated by a slash, e.g. +10/5. What does this mean?

[Necroticplague]

1. It's increased TO that number.
2.At 6,11, and 16 BAB, you get another attack when you full-attack at -5. This is represented by slashed (i.e, BaB +6 gives you and extra attack at +1. This is written +6/+1).

[Zanos]

To clarify, the classes base saves are increased to the listed number on the chart, but that stacks with the base save bonuses you may have from another class. So a Wizard 10/Fighter 5/Rogue 5(for whatever reason), would have +3/+3/+7 from his wizard levels, +4/+1/+1 from his fighter levels, and +1/+4/+1 from his rogue levels. His total base saves are +8/+8/+9. Then you add your ability score adjustments and any other modifiers, like a cloak of resistance, to those values, to determine what you're adding to your roll.