Numbers 11:28 NASB
28 Then Joshua the son of Nun, the attendant of Moses from his youth, said,
Moses only stayed for only a year in Egypt after his return from Midian before they left for Canaan
Moses and Joshua only met after Moses return from Midian.On their way to Rephidim that is when Moses enlisted the services of Joshua to lead the army.
There is no record of Moses being acquainted to Joshua before this.
So how was Joshua an attendant to Moses from youth when it seems they only been acquainted for a short time