I read the following statement in Introduction to Graph Theory by Douglas B. West:
If $\sum{p_i}-k+1$ objects are partitioned into $k$ classes with quotas $\{p_i\}$, then some class must meet its quota.
Several search on Google returns nothing satisfying. I don't understand what this statement means: how should I understand "partitioned into $k$ classes with quotas $\{p_i\}$"?