Editing Spec.isa (section)

==== Bit widths ====
Some operations (such as multiplication) will easily allow you to exceed the bit width of the virtual operand you're creating, or of the final output bytes.  The game will cause an error when that occurs.  Additionally, negative values are prone to being interpreted as 64-bit unsigned values (as 0f 0.1354 Beta) which can cause unexpected errors and odd-looking error messages.
When in doubt, mask out the result of your expressions to ensure they fit within the intended bit width, especially when working with signed values.