千 (qiān): A thousand. This character is used to signify a very large number.
变 (biàn): To change, to become different.
万 (wàn): Ten thousand. Like 千, this character is used hyperbolically to mean a massive, countless amount.
化 (huà): To transform, to -ize (like in “modernize”). It implies a deeper, more fundamental change than 变 (biàn).
The characters combine to create a powerful image: “a thousand changes and ten thousand transformations.” The use of both 变 and 化 suggests changes of all types, from superficial adjustments to fundamental transformations, and the numbers 千 and 万 emphasize that these changes are endless and innumerable.