"A suffix after the duration value to determine the time unit the duration applies to:
min = minute emin = elapsed minuteshr = hour ehr = elapsed hours
day = day edays = elapsed dayswk = week ewk = elapsed weeksmo = months emo = elapsed months
Note that the number of hours per day, hours per week and days per month values are set within the Calendar tab of the Options dialog box (Tools..Options).
SOURCE: project glossary-projectlearning.net"