In these notes, page $10$, bullet $(5)$, it is stated that if $X$ is a scheme of finite type over a field $k$, then the motivic cohomology $\mathrm{H}^{p,q}(X,R)$ of $X$ over $k$, where $R$ is a ring, vanishes if $q<0$. Is there a reference available online (for free) that proves the above-mentioned fact?
Thoughts
I think it has something to do with the Chow-groups-definition $\mathrm{H}^{p,q}(X,\mathbb{Z}) = \mathrm{CH}^{q}(X,2q-p)$, since if $q<0$, then $2q-p<0$, and hence $\mathrm{CH}^{q}(X,2q-p)=0$. However, I don't understand why it would hold for a general ring $R$.