In my American (English) version, the Help file states:
(emphasis mine)
<<<"If LOOKUP can't find the lookup_value, it uses the largest value in the
array that is *LESS THAN OR EQUAL TO LOOKUP_VALUE*.">>>
Now, my suggested formula uses an *extremely large* lookup value, which will
probably *never* exist in any lookup range (array), BUT ... and here's a
very significant BUT ... you should also remember that the lookup range is
supposed to be *SORTED, ASCENDING*.
SO ... If Lookup *can't* find that large lookup value, and it assumes that
the range is sorted, it *ALSO* assumes that the *LAST* number, not being
larger then the lookup value, *MUST* be the *largest value* less then the
lookup value.
That "quirk" in the Lookup function allows this type of formula to return
the *last* number in the lookup range, *NO MATTER* what it's actual value
might be.