Actually, that is a superseded reading of the darkvision rules. Later editions have clarified that darkvision only works at all within the given range, to keep in agreement with the monster manual definition. I wouldn't normally bring up a rules citation for a system, but since this directly relates to a setting in Roll20 (and its published 5e modules) here is the errata : “Within
a specified range, a creature with darkvision can see in dim light as if it were
bright light and in darkness as if it were
dim light, so areas of darkness are only
lightly obscured as far as that creature is
concerned.” So the RAW setting would be 60/0, but adjusted to your personal level of utility.