Ideally, you want a safe number to shoot twice a day.
For new folks, we suggest you don't shoot below 200 mg/dL or 11.1 mmol/L.
As you collect more test data and get it in the spreadsheet, plus add a signature block about your cat, you, and any special circumstances, you'll be ready to move into the Lantus forum and post there. Then, you'll drop your no shot limit to 150 mg/dL. As you get more comfortable, you may even learn to shoot low to stay low ... but not today! (I'm not up for staying up all night while you test him every 30 minutes and feed him high carb gravy!)