I have another question about this paper. There the authors prove a special version of the maximal flow-minimal cut theorem for uniform exactly-$k$-splittable $s$-$t$-flows. They define the cut in this situation on page 9.
If you have a partition $C\cup (V\setminus C)$ with $s\in C$ and $t\in V\setminus C$, the $k$-uniform cut capacity $c_k(C)$ is the maximal volume of a packing of $k$ identically sized packages into the bins with size corresponding to the edges from $C$ to $V\setminus C$. The minimum $k$-uniform $s$-$t$ cut, $c_k(s, t)$, is defined by $c_k(s,t):=\min\{c_k(C)|s\in C\subset V\setminus \{t\}\}$
My question is then about Theorem 7. How can we derive this lower bound of $k$ for a standard minimum $s$-$t$ cut in the graph $G'$?