Most of the major concentration camps had smaller camps attached to them. Some of these were at quite a distance from the main camp. Auschwitz, for example, had 3 camps on the main site and a further 45 sub-camps, many 20-30 miles away or even further.
There was 1,500 concentration camps. 20 of them were main camps and their were about 100+ more concentration camps but their didn't last long. Their is about 1,250+ sub camps, so this all ties along together.
You may be thinking of the Auschwitz group of camps, but there were others, too. There were several smaller forced labour camps, some of them temporary. For details of the main concentration and death camps in Poland please see the related question.
Many of the camps had satellite camps, some of which functioned for only fairly short periods of time. The Wikipedia article - see below - gives the names of the main camps and some information about the satellite camps.