Laertius gives (1)sensations, (2)feelings, and (x)anticipations and (3)image-based focus of the mind.
Epicurus himself says (1)sensation, (2)feelings, and (3)the whole visual focus of the mind
There is no discrepancy, but if there was, it is the anticipations that are the addition by Laertius -- because both mention (1)sensation, (2)feelings, and (3)mental focus.
there's no reason to split the term into two, and that it's best to think of there being only three categories
I don't think the fourth criterion is a mistake.
You are both correct. Fundamentally any and all sensation is our measure of truth -- we receive information from all impressions from the outside world that interact with our body.
10.51a [Hicks] For the presentations which, e.g., are received in a picture or arise in dreams, or from any other form of apprehension by the mind or by the other criteria of truth, would never have resembled what we call the real and true things, had it not been for certain actual things of the kind with which we come in contact.
10.51a [Bailey] For the similarity between the things which exist, which we call real and the images received as a likeness of things and produced either in sleep or through some other acts of apprehension on the part of the mind or the other instruments of judgment, could never be, unless there were some effluences of this nature actually brought into contact with our senses.
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The anticipations are just as momentary as your sight -- and your use of them can improve in the same way: over time you can increase your discipline/ability to focus on what is real, as Epicurus says "through the influences entering from the surrounding environment, taking the guidances towards improvement." (P.Herc. 1191 fr. 124).
Epicurus also says, in Book 25, P.Herc. 1056 col. 21 (fr. B 43) [Sedley 20C.1] From the very outset we always have seeds: some directing us towards these, some towards those, some towards these and those actions and thoughts and characters, in greater and smaller numbers. Consequently that which we develop – characteristics of this or that kind – is at first absolutely up to us; and the things which of necessity flow in through our passages from that which surrounds us are at one stage up to us...