c2d output Interpretation

[Nicholas Oleksinski]

Hi:
I am trying to design a digital phase lead compensator using the c2d function in the Octave 4.0.0 control package.
The output of the b & a coefficients I fed in looks like this:

      7.474 z^2 - 14.29 z + 6.829
 y1:  ---------------------------
         z^2 - 1.52 z + 0.5772

I noticed a couple things about this output:

1) The powers of the 'a' coefficients start positive.  Does that not make this system non-causal?

2) Why is this discrete time LTI model represented as "y1" and not "H(z)"?  I fed in the coefficients of H(s) by running c2d this way:

  comp_tf = tf(gain*numc,denc); %create the s domain LTI transfer function
  comp_tf_d = c2d(comp_tf,0.001); % sample at 1kHz

Thanks