Visa means an endorsement or an entry in a passport or other travel document made by an immigration officer or any official of the government authorized to do so to indicate that the bearer thereof has been granted permission to enter or er-enter the country concerned.
A visa in Malawi just grants permission to someone to enter into the country. Once it has been issued, it has to be used within the validity period from the date of issue. However, the validity of the visa is not the same as the authorized period of stay. The validity of the visa indicates the time period when entry is permitted into the country.