Person sized to … really big person sized. This is the scale at which PCs normally interact with their world. There aren’t any special rules governing personal scale.
The size of full grown trees to twice the size of trees. This is the smallest size for an organization. It can also represent properties, a village or small town. Things and organizations of this scale can interact with one another normally.
A person can interact in a limited way with things of this scale. A giant-sized creature would be broken up into zones and a person size creature could do things that might affect a zone, such as placing aspects via create an advantage actions. Zones that might describe a giant-sized creature can include head, torso, left arm, right arm, left leg, and right leg. Some characters might have stunts or extras that allow them to affect giant-scale creatures or organizations directly so that they can take attack actions against them.
When a giant-scale thing interacts with personal scale things, they usually affect whole areas. Use their skills as normal, but add an aspect to the zone as well. For example, if a giant-scale dragon claws at PCs in a zone, it makes one attack against which all in the zone must defend. Then, apply an aspect to the zone such as Rent Earth.
Even bigger! Ancient dragons, turtles the size of islands, cities, kingdoms and even empires can be represented at this scale. Giant-sized things can’t directly affect epic scale things in the same way personal scale things don’t usually directly affect giant scale things.
To something of personal scale, epic scale things are worth entire maps!
Using the above rules, you can easily create whole armies! A group of 50 to 100 competent warriors (double those numbers for less competent combatants) could be described by a single stat block that you declare to be of a Giant scale. An army of thousands or even tens of thousands could be described the same way but declared to be of Epic scale!