How is possible that an individual living 48 hours with two offspring achieve greater fitness than one wit 100

Answer 1

If your offspring continue the pattern of producing two offspring every 48 hours, then in only seven generations you will have 128 great-great-great-great-great grandchildren. This will take a mere two weeks.

On the other hand, if someone of the same species has a hundred children but it takes them longer than two weeks to produce them, then they obviously will contribute much less (genetically speaking) to future generations.