In the article there is clear information about the inflationary epoch as it is stated:
"In physical cosmology the inflationary epoch was the period in the evolution of the early universe when, according to inflation theory, the universe underwent an extremely rapid exponential expansion. This rapid expansion increased the linear dimensions of the early universe by a factor of at least 1026 (and possibly a much larger factor), and so increased its volume by a factor of at least 1078. Expansion by a factor of 1026 is equivalent to expanding an object 1 nanometer (10-9 m, about half the width of a molecule of DNA) in length to one approximately 10.6 light years (about 62 trillion miles) long.
The expansion is thought to have been triggered by the phase transition that marked the end of the preceding grand unification epoch at approximately 10−36 seconds after the Big Bang. One of the theoretical products of this phase transition was a scalar field called the inflaton field. As this field settled into its lowest energy state throughout the universe, it generated a repulsive force that led to a rapid expansion of space. This expansion explains various properties of the current universe that are difficult to account for without such an inflationary epoch."
However, it is also stated when it ends:
"It is not known exactly when the inflationary epoch ended, but it is thought to have been between 10−33 and 10−32 seconds after the Big Bang."
At that moment, the size of the universe was as big as grapefruit:
"Inflationary Epoch, from 10^–36 seconds to 10^–32 seconds:
Triggered by the separation of the strong nuclear force, the universe undergoes an extremely rapid exponential expansion, known as cosmic inflation. The linear dimensions of the early universe increases during this period of a tiny fraction of a second by a factor of at least 10^26 to around 10 centimeters (about the size of a grapefruit)."
So how can we explain the expansion from a grapefruit size to 4 light year size (in the first second)?
Where does this "grapefruit" stuff come from? It is not in the Wiki article I linked to.