Function fit_context_explained 

pub fn fit_context_explained(
    trained_ctx: Option<u64>,
    weights_bytes: Option<u64>,
    kv: Option<KvElemsPerToken>,
    k: KvCacheType,
    v: KvCacheType,
    budget_bytes: Option<u64>,
) -> (Option<u64>, FitInputs)

The same calculation, reporting what it worked from.