What Size Trucks Should I Buy For A 7.68 Skateboard?

For a Real Never Dead Med Skateboard Deck -7.68,
I want to buy Thunder Thomas 2nd Strike Lo 145 White/ Black.
Now, what does the 145 mean?
And what size is good for my board?
I found this chart but i did'nt understand what it means:
3.0
Fits Deck Sizes 7.0-7.4

3.5
Fits Deck Sizes 7.45-7.8

4.0
Fits Deck Sizes 7.85-8.25

5.0
Fits Deck Sizes 8.25-8.75

6.0
Fits Deck Sizes 8.75-9.25

so by the chart, i'm supposed to buy 3.5 right?
help please