Apple has made the decision to transition to 64-bit technology and is going to require all applications to be entirely 64-bit compatible in the future. While Hallmark Card Studio is 64-bit compatible and runs without issues on 64-bit systems, it includes some 32-bit components allowing it to also run on older Operating Systems.
If you are running the latest version of macOS High Sierra (10.13.4) - you will get a one-time alert when you first launch Hallmark Card Studio. Your application will continue to work without issues on your existing Mac. Please disregard this message. We are in the process of making Hallmark Card Studio entirely 64-bit compatible.
Please refer to this technical note from Apple for more information on their eventual transition to 64-bit applications: https://support.apple.com/en-us/HT208436