This read-only Counter64, in milliseconds, indicates total time for SharePoint pre-fetch Cache Misses since that optimization was started, with discontinuities possible at HTTP AO re-initialization, indicated by cwoAoStatsLastResetTime for the HTTP AO. An admin uses this to quantify the latency cost incurred when pre-fetched content didn't actually satisfy the client's subsequent request, requiring a fresh fetch anyway. A high miss time relative to the RTT saved value would suggest the pre-fetch prediction logic isn't well matched to actual SharePoint usage patterns at that site.