Yes, we did say that '{' was the election, but we discovered in message 6 that '[' was the mass of one electron. Since '!}!' is a constant times a mass unit, then '}' must also be a mass unit. Very similar to how we have the amu and then g (or kgs or lbs or whatever :-). And with the conversions to our unit system, the mass of TCEarth seems about right given size and all.