Postage Policy: What's the difference between selecting '2nd class' and '2nd class letter'

[strangestash]

What's the difference between selecting '2nd class' and '2nd class letter' on your postage policy? For some reason the former has a day extra lead time on item detail pages even though they're both listed as '2-3 working days'?

'Royal Mail 2nd Class Letter' shows:

'Royal Mail 2nd Class' shows:

[tommystrezures]

Letters are treated differently. Ebay will be presuming that 2nd class is parcel size. Current lead times according to our PO yesterday on Royal Mail delivering 2nd class letters is 3-5 days. Also rules were relaxed recently on when 2nd class is delivered, we certainly only get 2nd class letters a couple of times a week now in a bundle as opposed to every day.