He's being facetious, it's like this forum's trademark by now. Although a friend once convinced me it was the lightning from the Big Face that removed his fourth finger. I believed that for about a year.
Abe will have four fingers for the remainder of the series. The updated Mudokon model in Munch also has four fingers—although the moon irksomely still has only three. All that rubbish with the Japanese culture being offended, unless they get some sweet, sweet moolah, is long gone with the advent of digital publishing.