Numbers 4:35

35 All the men from thirty to fifty years of age who came to serve in the work at the tent of meeting,

Read Numbers 4:35 Using Other Translations

From thirty years old and upward even unto fifty years old, every one that entereth into the service, for the work in the tabernacle of the congregation:
from thirty years old up to fifty years old, everyone who could come on duty, for service in the tent of meeting;
The list included all the men between thirty and fifty years of age who were eligible for service in the Tabernacle,