Why do graphs in different areas show different results for the same metric?

by Sep 22, 2017

When looking in the overall view I see a sever wait spike going to 21,000 but when I switch to the Resources tab that same spike is only going to 6,000.  Which is correct and why do they differ?  This can really throw off my troubleshooting and I’ve seen it in other metrics.

…and WOW, I tried to insert some screenshots but this form only allows 64K for posts?  Really poor.