How many calories during pre op diet?

So I started my pre op diet today. It's 2 days full liquids then 1 day clear liquids. My doctor didn't really tell me how many calories to take in. He said I could even make smoothies with fruit in it if I wanted. I was super busy today so all I've had is 3 ready to drink protein shakes and a can of low fat cream of chicken soup with 1 cup of fat free milk in it and a scoop of unflavored protein powder. Mfp says I've had 835 calories today. I feel like crap but expected to feel worse. Should I have some more calories tonight or stay where I'm at? Also was yogurt allowed on your pre op diet? I think I will email the nut tomorrow but I was just curious what your thoughts were. 

 Edited to fix silly typos.

Thanks!

I think 1200 is the usual amount, although some people are put on an 800 plan.

I didn't count calories during my two-week preop diet.  I just focused on doing what I was told to do and on trying not to be too much of a ***** due to the changes it brought.  Those were quite enough to worry about for me.  :)

Just worry about following your preop diet plan, and you'll be fine.  It's normal to feel like crap during preop.