The MATLAB regular expression syntax is documented here:
and it does not include any operator '\P'. In any case you have not given us any information about what data you want to obtain from the string: is it the second number value, or all of the string within parentheses, or both number values... is the colon always present, or could it be a concatenation operator instead? You state that "only interested in the data if the value to the left of the colon is a zero", but what is "the data"? Even parentheses could be data. It is only worth starting to write a regular expression once you clearly specify the requirements it has to meet.
You could start with something like this, which returns the number the follows '0:'
>> str = '(0:20)';
>> regexp(str,'(?<=0:)\d+','match','once')
ans =
20
Bonus You might like to download and try my FEX submission:
which lets you interactively develop regular expressions and see the outputs change as you type/alter your expression.
