By Matthew Narvaiz / Journal Staff Writer   Analytical lab manager Calen McKenzie explains the readout of results from a test of a sample of cannabis at the Rio Grande Analytics lab in Albuquerque. (Liam DeBonis/Journal) If a customer walks into a licensed New Mexico dispensary to buy an eighth (3.5 grams) of flower today, they'll see more than the product's name. They'll see a label that will show potency levels to let the customer know how much THC — or tetrahydrocannabinol, the main psychoactive component in cannabis — is in the product. The label is also an indicator that...