YSK that if you are traveling westbound on even numbered highways or southbound on odd numbered highways, the exit numbers usually match with the miles left to the next state border.
from /r/YouShouldKnow
YSK認爲，如果你在偶數公路上向西行駛或在奇數公路上向南行駛，出口號碼通常與到下一個州邊界的剩餘里程相匹配。