This is the maximum size of LSPs and SNPs originated by this Intermediate System at this level, following the replaceOnlyWhileDisabled behavior. Lowering it forces the router to spread a large topology database across more, smaller LSP fragments rather than fewer large ones, which can matter on older or memory-constrained neighbors that cannot handle bigger LSPs, and IS-IS must be disabled at that level before this value can be changed. For example, reducing this from a modern default down to a conservative legacy value forces the router's originated LSPs to fragment into more, smaller pieces to stay compatible with an older neighbor that cannot process oversized LSPs.