It seems you are on the lowest dose judging by this:
Propranolol tablets come in strengths of 10mg, 40mg, 80mg or 160mg. The slow release capsules are 80mg or 160mg. The liquid comes in strengths of 5mg, 10mg, 40mg or 50mg in 5ml.
anxiety – 40mg taken once a day which can be increased to 40mg taken 3 times a day
It looks like you can increase it as your dose does not sound enough for anxiety.