Hi, and welcome,
@flower2024 ,
They're different tests. The 140 was likely your HbA1c, and it is measured in mmol/mol rather than mmol/l. It lets you know the average of the past three months, more or less, so that means that on average your blood sugars have been quite high, over all. The test you do at home is a test of what your blood sugars are doing right at that moment, which is measured in mmol/l. Hence the difference.
Your blood sugars should, ideally, not go over 8,5 mmol/l after a meal. It's over that when the damage starts to happen, especially if your blood glucose stays elevated for a long-ish time. When you eat, test before the meal and 2 hours after the first bite. You're aiming for a rise of no more, and preferably less, than 2.0 mmol/l, which would mean your body could cope with what you put into it. If it's higher, well... Then it couldn't process the amount of carbs consumed effectively.
I saw your other posts, and yeah.... Beer is often called liquid bread, meaning there's a lot of carbs in there, and apples are iffy. Some here can have them, I know I can't. Test, and see what is true for you, specifically.
https://josekalsbeek.blogspot.com/2019/11/the-nutritional-thingy.html might help a bit as well. Keep in mind though, while we extol the virtues of low carb eating here quite often, combining it with Jardiance might cause hypo's: that's why you were given a meter when many of us don't get one. The medication you're on can make your blood sugars go too low, mainly if combined with other diabetes medications though, from what I gather. (Since your profile states you're "diet only" but you mention Jardiance in your post, you might want to edit your profile to correct the treatment you're on. To avoid us giving potentially harmful advice, not just being nosy). So if you change your diet, do be careful, as you might need to adjust your dosage or treat for a hypo. Keep something with fast acting sugars handy. Like honey, orange juice, that sort of thing.
Hang in there eh. I know it's a kick in the head, and a very, very steep learning curve, but you're asking the right questions.
Good luck,
Jo