I have used small, "undersized" males a number of times when I really needed to get them in the genepool that year instead of waiting. This year, I used a young ultra caramel male that was small, but willing. He bred about 4 or 5 females, but most of the eggs were infertile. However, a few still look good.
Using such males in the past, I have sometimes found that even if most of their eggs were bad, there were often a few good ones too. And the following year, he usually did MUCH better in the fertility dept.
OTOH, I have found that many of those little bitty males did just fine and produced lots of good eggs their first year. So my guess is that the male was mostly shooting blanks, but that any fertile eggs are most likely his, and that he will most likely do much better next year.