Here is a link to understanding how that works.... It explain it far better than I can. Good luck.
http://www.crfb.org/papers/updated-appropriations-101-1
Well, I read through it and what it seems to say, relating to the wall money being authorized (the first part of the process which determine the total amount of money to be spent) and the actual appropriation which is actually spending of the sum (on the wall)was only half done.
In other words the money part of the total budget but it was never actually directed to the wall(appropriated) after the budget was signed.
In this light it seems you are right because the signed budget is just for one year.