Your diet and your levels look absolutely fine, please don't let your meter fuel your anxiety. It's a useful tool but it's not accurate enough for you to worry because it measures a 6 and you think it should be lower
( 6 after exercise is a good result) your meter is only accurate to plus /minus 15% so your actual level could be much lower than 6.
Our bodies are not machines they are complex living organisms controlled mainly by hormones. Exercise can cause higher levels because hormones can signal our liver to release some stored glucose to give us a little energy for the exercise. In exactly the same way it can give us a little boost to help us start the day (Dawn Phenomenon) our levels are quite dynamic changing throughout the day. It's not going to help your anxiety or your levels if you get stressed every time they are not what you think they should be