T'hilas Hashem, the standard sidur (prayer book) of the Lubavitch chasidim, includes, passim, rulings of their first rabbi ("the Rav"), copied from his own sidur. The rules printed before halel indicate that one should, on Sukos, shake the lulav in a suka before the prayers begin. If one did so, they continue, then he should shake it four times during halel: once during the first appearance of "hodu", twice during "ana", and once during the last appearance of "hodu". However, if he failed to shake the lulav before the prayers started, then he should shake it before halel and then only three times during halel: once during each appearance of "hodu" and only once during "ana". It cites "R.M." (Ra'ya M'hem'na?) as a source.
Why does the number of shakings of the lulav during halel differ, according to the Rav, depending on when one previously shook it? Why does he prescribe fewer shakings during halel if it was shaken in the synagogue immediately before halel than if it was shaken in suka earlier?