yea I think the default is 200
There you are talking about the internal CSF block table - I normally have that set at 800, and 1000 on my main servers. I ALWAYS turn on ipset (ensure it is installed though normally is by default). I uncomment most of the lists in csf.blocklists and add about 8 country blocks. This is on VPS with 1GB to 4GB RAM, on 4 different control panels.
ipset list -o save | wc -l
66297
That's the number of entries, of which some are network blocks, not just individual IPs. I think I should reduce that number on that particular VPS; others are around 55k entries.
In short, it looks as though you have something amiss with your environment.