Well, your runway length must be equal or greater than RLD.
E.g.
RLD 2004, RWY length 3000 - O.K
RLD 2004, RWY length 1800 - not o.k.
Look at it this way:
ALD is what your airplane can do under current conditions, assuming short touchdown and maximum braking
RLD is the minimum runway length required for dispatch, with an added margin of 67%
Actual runway length is what your airports has...
ALD values can be surprisingly low, 1200m is not uncommon to see on a dry runway, even on a widebody - but that assumes a perfect landing and maximum braking effort right away - which is not something you normally do in day to day operations. That’s why you have margins and that’s why for inflight calculations you use OLD (operational landing distance), which has much more conservative values.