Because y = 4 is the asymptote?
I have no clue what you mean by this. What do you mean by "values for 4"? My first thought was that "for 4" meant "for x= 4" but that's easy to calculate- if x= 4, then $\displaystyle y= (1/4)^4+ 4= \frac{1}{64}+ \frac{256}{64}= \frac{257}{64}$. If you mean "there exist x such that y= 4", it is not true. If $\displaystyle (1/4)^x+ 4= 4$, then $\displaystyle (1/4)^x= 0$ and there is no such x.