How to calculate sluster size distribution in gromcs?

Dear GMX users,

There are a several water/zeolite systems with different water loadings. I want to study the effect of water loading on cluster formation (Number of clusters, …). However, for a single system, I would like to obtain a plot of cluster size distribution. I mean I would like to know the probability of a cluster size of (for example, 10 water molecules). There is a histogram as an output of gmx clustsize but it is not what I need because it just shows a simple distribution of cluster size of 1.

I need a distribution of different sizes. How can I get it?

Thanks for your help