Is the stardust column the amount to get to that level or the amount it will say on your screen to get to the next level? I would know for sure is the first row was empty or the last row. How can it list 200 to get to level 1? are there level .5 Pokemon?
Stardust is the power up cost at that particular level. 200 stardust for level 1, 1.5, 2, 2.5; 400 stardust for level 3, 3.5, 4, 4.5; etc
Each time you power up once, your Pokemon gains half a level, so indeed Pokemon can have level .5! As a tangent, wild and hatched pokemons always come in whole number levels, never half levels.
I am a level 21 Trainer with a Vaporeon that says 3000 to power up, but it is grayed out. So is my Vaporeon 22 or 22.5?
Pokemon level is capped at Trainer Level + 1.5, so your Vaporeon is level 22.5. Once you level up to 22, you would able to power it up two more times to level 23.5.
You're right to point out the chart was a little confusing. I updated it to show half levels now. Hope that clarifies it a little for the future!