How big should my plant get under a T5 light?

How big can you get a plant to grow under a 24x28 T5 light? Need to know how big the plant can get under this light before the plant starts to struggle and would need to be placed under a more powerful light or trying to bud it.

You can grow one plant maybe 3' tall with that light system.
Keep the light centered over you plant, and 2 or 3 inches above it with a fan blowing to keep heat from building up, and you will be straight.

i have one kitchen and bath t5 and its been a few weeks and mines 5inches high