x1 is a store/deposit/supply/reserve of materials/energy x2 in containment x3.
x3 need not be a container, but could merely be a site/location restriction; e.g. a heap. The sumti indicates how the supply is identified and distinguished from other occurrences of the stored x2 that are not part of the store. (cf. panka; vreji for information storage; sabji for a store or reserve that is not necessarily tied to a site, banxa, panka)