In my opinion, Amber tends to track the acidity pattern of Munich and Biscuit and Aromatic malts (color for color). It does not appear to be quite as acidic (color for color) as for a caramel/crystal type malt.
IMHO, a quasi-workable kludge (to sort of level the acidity playing field) appears to be to enter amber as caramel/crystal, but falsely reduce its Lovibond color by perhaps about 1/3. But why settle for a kludge?
Example of the kludge: Enter 30L Amber as 20L Caramel/Crystal