Exponential growth resulting from an entity giving birth to new entities, which in turn give birth to other new entities.  Multiplication is not the same as serial addition.

The verse 2 Timothy 2.2 provides strong insight into multiplication, as is reveals 4 distinct generations: 

1. Paul, speaking to
2. Timothy, who entrusts to
3. faithful men (plural), who teach
4. others also (plural)

The result is a mimimum of 8 entities: Paul, Timothy, at least 2 "faithful men," and at least 4 "others also."