I know it has something to do with the size of the exe file's header but I don't exactly know how it works in DOS files. Exactly how that value is calculated I don't know. These references are a way for the program to refer to data located in a different section, and are basically the offset of that data in the file + a fixed value. as I said, in C&C1 the unit data is actually in a program code section) More specific, you got actual program code sections with instructions and you have pure data sections, where constants (like the data my editor edits) are stored.
See, an exe file is separated in several sections.
Eh, well you'd have to see that in a disassembler to let it make sense.