Complex sentence: In some US states, an alternate route will be designated by adding an "A" after the number instead of a sign marked "Alternate" above it: "US 69A" means "US 69 Alternate".
Split into simpler sentences: In some US states, an alternate route will be designated by adding an "A" after the number instead of a sign marked "Alternate" above it. Example: "US 69A" means "US 69 Alternate".