Depending on if you actually need functional Codas in the same project or not, setting this to something really small like 1/100 of a space works too. Anything other than 0 will then let you adjust the functional Coda indentation if it’s on the same system as the preceding music, and 1/100 is unnoticeable at the beginning of a system. If it’s just for exercises, and you won’t need a functional Coda too, then 0 is fine.