showCategory parameter for visualizing compareCluster output

I am using dotplot() to visualize results from enrichGO(), enrichDO(), enricher() and compareCluster() in clusterProfiler R package. When specifying showCategory, I get the right number of categories except with the results of compareCluser().

In my case, I use compareCluster() on a list of 3 elements:

str(ClusterList)
List of 3
 $ All : chr [1:1450] "89886" "29923" "100132891" "101410536" ...
 $ g1  : chr [1:858] "89886" "29923" "100132891" "101410536" ...
 $ g2: chr [1:592] "5325" "170691" "29953" "283392" ...
CompareGO_BP=compareCluster(ClusterList, fun="enrichGO", pvalueCutoff=0.01, pAdjustMethod="BH", OrgDb=org.Hs.eg.db,ont="BP",readable=T)

dotplot(CompareGO_BP, showCategory=10, title="GO - Biological Process")

I ask for 10 categories, but I get 15 categories in All, 8 categories in g1 and 12 categories in g2. None of the categories, neither the sum of the categories are 10…

Is the option showCategory working in the case of comparison? Am I missing something here?

And which categories precisely will it plot? the most significant whatever my 3 cases or the most significant of each case?

The question was posted in Bioconductor support site. It seems quite confusing and I think I need to write a post to clarify it.