Here the 1841 British edition replaced the plural possessions with the singular possession (the last s in the word was set upside down, thus the symbol ~s ). The subsequent LDS edition (in 1849) restored the original plural. As explained nearby under Helaman 4:8, the Book of Mormon text allows for some variation in the grammatical number for the noun possession(s). For discussion of variation in the related phrase “the land(s) of one’s possession(s)”, see under 2 Nephi 29:14. For each case of possession(s), the critical text will follow the earliest extant reading, thus “the half of all their possessions” here in Helaman 4:10.
Summary: Maintain in Helaman 4:10 the plural possessions in the phrase “the half of all their possessions”, the reading in 𝓟 (here the earliest textual source).