Lerna Ekmekcioglu's session from Monitorama PDX 2023. We look at availability, throughput, latency as indicators of health of our systems. Aggregations on top of these measurements help us further reason about their well being by zooming out and looking at how they behave given a meaningful slice of data. We talk about p50, p90 or p99 latency. We use graphs with logarithmic scale. But do we actually understand the math behind these and how to use them with ease? In this talk, I will deep dive into just the math you need to know for monitoring.