What does Exodus 9:6 mean?

Prior verses explained the Lord's pronouncement of a fifth plague (Exodus 3:20; 9:1–5). Exactly as prophesied, the pestilence strikes, apparently with an incredibly rapid effect. Also as promised, this only affects Egyptian animals, leaving Hebrew flocks untouched. Both Egyptians and Hebrews would have recognized this as supernatural. This could not have been an unusual disease or natural occurrence. The God of the Hebrews was showing His power over the false gods of Egypt.

The expression "all the livestock" in this passage is probably not meant to mean that every single last animal died. The following plagues are still said to impact Egyptian livestock (Exodus 9:9, 19–21). Even in modern speech, a farmer who loses 95% of his flock would probably say, "'all' my cows died." When tragedy strikes, one might say that "everyone in the world is mourning," which will never be true in the most literal sense. Further suggesting this idea is that later verses use precise language when noting that "not one" of Israel's animals died (Exodus 9:7). Egyptian animals impacted by the next plagues were likely the few which survived this pestilence, plus any the Egyptians were forced to buy from the Hebrews.