Regex to exclude specific characters

Your pattern first matches from { till } and then matches in a non greedy way .*? giving up matches until it can match a p, dot space and 1+ digits.

It can do that because the dot can also match {}.

You could use negated character classes [^{}] to not match {}

\{[^{}]*\}[^{}]+p\. [0-9]+

Regex demo