 Tachyon condensation transforms such a pair of bundles to another pair in which the same bundle is direct summed with each component in the pair.Thus the tachyon condensation invariant quantity, that is, the charge which is conserved by the tachyon condensation process, is not a pair of bundles but rather the equivalence class of a pair of bundles under direct sums of the same bundle on both sides of the pair.This is precisely the usual construction of topological K-theory.