Image field - Cant set up number of values
If you're using the same image field on two content types then the cardinality (number of values) will be the same across both. 

You'll notice you have 'instance' settings and 'field' settings on the field edit form. The 'instance' settings are unique to that instance, and can be different for each entity type/bundle the field is attached to.

The 'field' settings are global to that field, and the cardinality is one of these global field settings. If you change it for one content type, it will automatically change for the other content type. The caveat to this is that if you have data in the database for those fields already, you might not be able to change the cardinality at all (the select list will be greyed out).

This is by design, and how the field system works (there's no way around it). If you need to have two fields on two different content types with different cardinalities, you need to create two separate fields.