it appears based on other canon units not evenly divisible by 20 like the Mantis L (30 tons), Nyx 90 (30 tons), Ryoken III-XP D (55 tons), and Hachiwara 6P (70 tons) that the weight and size of the lance is rounded up to the next 20 ton increment. unsure if that's how it's supposed to work based on the wording in TO, but that's certainly how it's done in practice