How can I get the full coefficient at c2d command?

Version : R2006a

>> H = tf([1 -1],[1 4 5],'inputdelay',0.35)

Transfer function: s - 1 exp(-0.35*s) * ------------- s^2 + 4 s + 5

>> Hd = c2d(H,0.1,'zoh')

Transfer function: 0.04405 z^2 - 0.01434 z - 0.03792 z^(-4) * --------------------------------- z^2 - 1.629 z + 0.6703

Sampling time: 0.1

>> [num den]=tfdata(Hd,'v')

num =

   0.04405355284555  -0.01434015623591  -0.03792120199524

den =

   1.00000000000000  -1.62928101910761   0.67032004603564

but actually denominator is 6th order. how can I get the coefficient?