28:4a בין הערבים = between the settings.  It says in vs. 3 that two lambs are to be offered "to the day".  The lambs are numbered "first" for the morning, and "the second" for "between the settings", which is mid afternoon on the same day.  The first setting point is at noon, and the second setting point is at sunset.  The period between is called "between the settings", which corresponds to the English "afternoon."