What does the numeric NTP stratum level indicate?

NTP stratum is a measure of the distance from a reference clock. A stratum 1 server is directly synchronized to an authoritative time source (like a GPS receiver or atomic clock). A stratum 2 server synchronizes with a stratum 1 server, and so on. Therefore, the stratum level directly indicates the number of NTP hops (or synchronization layers) away from the primary, most accurate time source. The amount of offset or drift between the device clock and true time are metrics related to clock accuracy and stability, but they are not what the stratum level represents. While a lower stratum generally implies better accuracy, the stratum itself is a measure of hierarchical distance, not a direct measure of offset or drift. The "number of hops it takes to reach the primary time server" is close, but "authoritative time source" is more precise as stratum 1 servers are directly connected to these, and subsequent strata are hops away from that ultimate source.