Actually,
There is NO DEFAULT value of this item in eos github repo. what you said "default" value 1024, it is from eos-bios created by eoscanada. when launching the eos mainnet, many bps used this config.

But there are little peoples can explain what it really means. And No One explains this item and value, or suggest the value. Maybe it won't affect this good project and the good community, and the price of EOS.