You're getting the microgram statement from here. You miss the point. A millionth of a gram is feasible to make and contain right now. It was predicted by 2010 in the paper using CERN, and there are much better facilities producing since then.

You're missing the point to be pedantic over a 20 year old paper. Newer approaches reduce the antimatter requirements for such weapons even more.

This might make you wonder why antimatter is being transported around. The fact is, proposals to weaponize antimatter as a fusion trigger have been around for over 40 years, and the means to achieving that from a production and engineering standpoint seem a good bet to be available today.