When they return to earth, how long will they have been gone, according to the three ladies?

Mrs.
Whatsit says,

we'll have you back about five minutes
before you left, so there'll be time to spare and nobody'll ever need to know you were gone at
all.

Mrs. Whatsit tells them this after they have all
tessered, or used wrinkles in time, to travel across vast distances of space. They are about to
visit with the...