Constant AVERAGE_HEADER_SIZE 

pub const AVERAGE_HEADER_SIZE: u32 = 1024;

Average header size in votes_ancestries field of justification on Polkadot-like chains.

See bp_header_chain::ChainWithGrandpa for more details.

This value comes from recent (December, 2023) Kusama headers. Most of headers are 327 bytes there, but let’s have some reserve and make it 1024.