Option 1: Under the rule of Mahmud Gawan, the Bahmani Kingdom was divided into eight provinces or Tarafs. This allowed for better governance and administration of the kingdom.

Option 2: Mahmud Gawan implemented a reform measure where the nobles of the kingdom were paid salaries. They were also required to maintain contingents of horses. This measure aimed to strengthen the military power of the kingdom and ensure the loyalty of the nobles.

Option 3: This option correctly states that the setting apart of a tract of land called Khalisa for the expenses of the Tarafdar was not a reform measure carried out by Mahmud Gawan. Khalisa was actually a fiscal land grant that was given to government officials or nobles to meet their household expenses. This was a pre-existing practice in the Bahmani Kingdom and not an innovation introduced by Mahmud Gawan.

Option 4: One of the key reforms introduced by Mahmud Gawan was the measurement of land and the fixing of land taxes based on that measurement. This aimed to bring fairness and efficiency to the system of taxation in the kingdom.

In conclusion, option 3 was not a reform measure carried out by Mahmud Gawan.