How to use precomputed distance matrix and min_sample for DBSCAN clustering method?
DBSCAN does not guarantee a minimum cluster size. There are known situations, c.f. Wikipedia, where a cluster can have fewer than "minPts" points. Furthermore, it has the concept of noise: points that do not have enough neighbors.

For epsilon, also see the Wikipedia article. As you don't specify the number of clusters, this parameter is what mostly controls how many clusters you get. Set it to 0, and everything will be noise. Set it to the maximum distance, and everything will be in one cluster.

Really read the article. It's about density, not about cluster sizes.