7:4 in seven days. A hundred and twenty years were needed to build the ark (6:3 and note) and one week to fill it. A Babylonian flood account imagines seven days to build a ship much bigger than Noah’s and a flood lasting seven days (6:15 note).
forty. Forty is a conventional number for a long time and signals the introduction of a new age: by Noah, Moses (Ex. 24:18); Elijah (1 Kin. 19:8); Christ (Acts 1:3). The forty days are part of the 150 total days (8:4).