Simplify the following text for a Grade 5 native English-speaking person.
Original: Among other reasons , this idea fails because there is no `` last 9 '' in 0.999 ... However , there is a system that contains an infinite string of 9s including a last 9 .
Simplified: 0.999 ... is a repeating decimal , which means the digit `` 9 '' is repeated forever . It is different from 0.999 , which only has three 9s .