A JB4 export is a table of what the recorder sampled. It is great for following channels over time. It cannot answer every question people want to ask of a car.
Start with the header and the export’s notes. A column called Boost has whatever meaning and unit the logger assigns it; Target, ECU Boost, and additive target values may describe something else. Keep the original labels and units until their definitions are verified. The Telemetry Lab does this instead of silently converting unfamiliar fields.
Time matters. Samples can arrive at uneven intervals, so drawing each row as an equally spaced second can bend the story. Keep the provided timestamps. A blank value is missing data, not zero. And smoothing a sharp change can make a graph prettier while hiding the part worth inspecting.
Read channels together. RPM and throttle help put a boost trace in context; target-like channels can be compared only after their meaning is clear. A peak by itself says little about road grade, gear, fuel, temperature, or recording conditions. It is a place to look, not a complete explanation.
The bundled demonstration has 92 samples over 119.97 seconds. Its recorded Boost channel reaches 17.5 psi and the file contains Map value 2. Those are measurements in this export. They are not a dyno result, a horsepower estimate, or a verdict about mechanical safety.
When comparing runs, check that the channels, units, maps, conditions, and sampling are comparable first. Then state what changed in the file. Let a controlled test answer the bigger performance question.