In the context of NVIDIA GPUs, “application clock” has a very specific meaning. It looks like here we are actually talking about “GPU clock” as dynamically adjusted by the GPU’s power management and clock boosting heuristics.
It is not clear what “max” refers to. Every GPU has a nominal operating frequency, and if environmental factors allow, and with GPU in power state P0, the GPU may be boosted above this level up to some maximum boost clock. What is the maximum GPU clock achieved by the T4 in this case? I have never used a T4 but some other Turing based cards can boost to 1800+ MHz, but in normal operation are more likely to run at 1500-1600 MHz.
On modern GPUs, it is rare that the maximum boost clock is sustained for longer than a brief moment. The most common limiters are power consumption and temperature.
The power management of NVIDIA reacts quite quickly to reduce clock boost if the nominal power limit is exceeded, although very brief excursions above the limit may occur (e.g. one might see 78W on a GPU with a power limit of 75W). Often boost clock is being reduced before the power limit is reached. For example, on one of my GPUs with a power limit of 75W, that appears to happen as soon as the power exceeds 65W.
The temperature limit is different based on GPU, typically when temperature reaches 83 to 85 degrees Celsius a significant boost clock reduction occurs, and generally any GPU temperature above 60 degrees Celsius or so negatively impacts achievable boost clock. Some people install very elaborate third-party cooling solutions on their GPUs for this reason. In the winter, I sometime accelerate my GPUs by dropping ambient temperature to about 10 degrees Celsius by means of cracking open the window in my office.
A third reason, more rarely encountered, has to do with GPU voltage. In order to boost the GPU clock reliably, an increase in operating voltage needs to be applied. If the maximum voltage supported (usually around 1 volt) is reached, or if voltage levels become unstable before that, boost clock will be reduced.