In a curious moment, Q states that humans aren't supposed to be in the Delta Quadrant for another hundred years - implying that, in a hundred years' time or so, the expansion of the UFP will bring its patrols and explorers to the Delta Quadrant.
In the mean time, the Federation "consists of over 150 worlds who have agreed to share their knowledge and resources in peaceful co-operation."
Territory "hundreds of sectors" across in "The Swarm" would take 15 months at maximum warp to circumscribe.
This implies the sector is a standard sized unit in cartography, as no prior political division of sectors by Voyager could have occurred.
Also in "The Swarm," the crew of Voyager develops a technique for sliding through a tachyon detection net, by refracting the beams around Voyager's shield.
The Nikrit Expanse is a vast area of space thousands of light years across; many Delta Quadrant races appear unclear on what lies beyond it or within it. This is Borg space. Within the heart of it, the Borg control thousands of solar systems, all occupied and settled by the Borg.
"Dragon's Teeth" - the DeVore claim 11 systems across three sectors.