Fuel flow rate through an injector is affected by a number of different things. This page focuses on the effects of the ECU's internal driver circuitry. Differences in design can influence how an injector responds. This adds yet another layer of difficulty to getting usable numbers from an injector testing service. If they're not using the same driver circuitry as you're using, then the numbers (primarily deadtime) aren't going to mean much to you.
Unless your injectors are being flow tested using the exact same drivers as are found inside your ECU, you can expect to see different behavior (primarily deadtime) when installed inside your car. One would expect differences in behavior when comparing drivers as different from each other as a 4/1 peak-hold vs. saturation style driver, but even drivers of the same “style” can produce significantly different results just from varying component selections in the circuit design.
We've measured a good 100-200 usec difference in deadtime comparing EVO8 and DSM (pre-98) drivers, for example. The exact difference depends on the combination of injector and ECU driver implementation.