Final answer:
Glucose reabsorption is occurring at a rate less than its maximum, as the transport maximum is higher than the current rate of glucose passing through the renal tubule.
Step-by-step explanation:
If no more than 300 mg of glucose is passing through the renal tubule every minute, and the transport maximum for glucose reabsorption is 320 mg per minute, we can conclude that glucose reabsorption is occurring at a rate less than its maximum. This is because the amount of glucose currently being reabsorbed is below the threshold where all the glucose transporters would be saturated and thus is not reaching the maximum possible rate of glucose reabsorption by the kidneys.