That 73 you got near the middle of the cycle on 3/7, while a nice looking number, was after at least 1, if not 3, doses of 4 units. The 371 after that is very probably due to compensatory hormones kicking in to protect your cat's life and releasing stored glucose to bring up the levels to safety.
Please consider stepping back to maybe 3 units if you're using the pen and 2.5 units if you can get syringes (preferred).
Always test before you give insulin; if below 200 mg/dL, wait without feeding for 30 minutes and re-test. If above 200, go ahead and shoot. Otherwise, post on FDMB and ask for feedback.
Tests between +5 to +7 show how low the glucose is going. For safety, that should stay above 50 mg/dL. If it goes below 50, you need to intervene to get the numbers up (see link for HYPO below).
In case you didn't get this already:
[Glucose reference ranges are unsubstantiated and have been removed by Moderator]
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Examples of using the chart:
Ex. You are a new insulin user and you test your cat before giving insulin. The test is 300. It probably is safe to give insulin.
Ex. You are an established user of Lantus, following the Tight Regulation protocol. You've tested around +5 to +7 to spot the nadir. It is 200 mg/dL. You probably need to increase the dose, following the instructions for the protocol.
Ex. Your cat is acting funny. The eyes are a bit dilated. You are concerned and test the glucose. The number is 35 mg/dL. ACK! The cat may be in a hypoglycemic state. You quickly follow the HYPO protocol linked in the glucose reference values chart. (which we really, really, suggest you print out and post on your refrigerator.)