If a value is stored as a 2-byte integer, you cannot overwrite it with a 4-byte value without shifting the rest of the file data, which will corrupt the save.

Editing any .sav file carries a risk of corrupting the file or breaking your saved game entirely. Always, without exception, make a backup copy of the original .sav file before you make any changes. This simple step ensures you have a working version to fall back on.

A minority of indie games use plain text formats masquerading under the .sav extension. Right-click the .sav file.