Some mushrooms can be poisonous after 24h, just in case. angel wing mushroom shows no digestive symptoms but encephalopathy after 2 day to 1 month of latent period. The mushroom was known to be edible for a long time. Were it not for full screening for encephalopathy cases (enforced due to SARS spread back in 2004), it could’ve remain “edible” still now.
Japanese use JIS but A size is the same with ISO so there’s no confusion here. For B size there’s slight difference in JIS and ISO, but as end user I hardly print anything other than A4 so haven’t encountered problems myself.