source: The games sold over 60,000 copies by February, but by April the games sold over 100,000 copies.
target: The games sold over 60,000 copies. That was copies sold by February. However, the games sold over 100,000 copies by April.
references: The games sold over 60,000 copies. That was copies sold by February. However, the games sold over 100,000 copies by April.