American amber ale's style range runs roughly 10-17 SRM — solidly in copper-to-light-brown territory, clearly darker than a pale ale but well short of a brown ale or porter. It's one of the narrower colour bands in common style guidelines, which makes hitting it a matter of real precision in the specialty-grain percentage, not just "add some crystal malt."
A real grain bill, computed
4.1 kg (about 9 lb) of pale base malt at 2°L, plus 0.5 kg (about 1.1 lb) of crystal malt at 40°L, in a 19 L batch, computes to roughly 8.4 SRM — just under the amber range's low end. Check this exact grain bill, and notice how close this recipe already sits to the amber threshold despite the crystal malt making up only about 11% of the grain bill by weight.
How little it takes to move this range
Because amber ale's window is narrow (10-17 SRM, a span of only 7 points), a fairly small change in crystal-malt weight or Lovibond rating moves a grain bill in or out of range. Bumping the crystal malt addition from 0.5 kg to roughly 0.75 kg in the same base recipe would push the same batch to just over 10 SRM, into the low end of the amber range — a change of only 0.25 kg (about 9 oz) deciding whether the beer reads as a "pale ale" or an "amber ale" by colour alone. This is a useful thing to know when tuning a recipe: at the amber-ale scale, specialty-grain weight is a fine adjustment, not a coarse one.
Amber vs. its neighbours on the colour scale
Amber sits between American pale ale (roughly 5-10 SRM) and brown ale/robust porter (roughly 20-35 SRM) — a beer computing in the high single digits reads closer to "gold" or "pale amber" in casual description (see the SRM to beer colour name chart), while genuine amber character needs the full 10+ SRM the style guideline specifies. If your amber ale recipe is computing lighter than the style range, the fix is almost always more crystal or specialty malt percentage, not more base malt.
Checking your own recipe
Run your actual grain bill through the SRM calculator and compare the result against the amber ale style page rather than assuming a recipe labelled "amber" automatically lands in range — as this worked example shows, it's easy to come in just under a narrow style's colour window without a specific check.