They always mean steps - you never give a numerical bonus or penalty to an action or skill check. See PHB p.12, "A +1 step situation penalty means..." Sometimes they will state something in terms of the final situation die step, but (errors aside) only when it's the final outcome. They don't always bother to say "+X steps" but just say "+X" for brevity, but it's the same thing - see the Mad Dog Morgan example on p.49 where they are showing how to do task checks and refer to him having a "+7 penalty" and showing how that is a +4d20 situation die.
So it makes sense to say a given NPC has a +d8 on a check, but only makes sense to say, for example, that some armor incurs a +3 action check penalty on its wearer (because it could stack with something else, you don't put a +d8 from it along with a +dsomething from another effect - there's only one net situation die level).
Just ask yourself "is this an action check" and if the answer is yes, it's a step. A +1 would be a flat number on a roll that's not an action check, like damage or armor soak.