I think before checking the fluid you should put the transmission selector level in all positions from P to L at least five seconds, bring it back to P again in the same manner, wait for two minutes, and then check the fluid level while the engine is running. Doing anything straying from the above made me have inconsistent readings. If you have the haynes manual do exactly how it says. If you don't have it I can send you the procedure when I go home tonight. (Provided that I don't forget)
ihsan