Hello Julia ,
The phrasal verb " make out " has several meanings.
In your sentence " Glad you could make it out" , 'make out' could be equivalent to some of those meanings as follows :
- comprehend or understand:
Glad you could make it out = Glad you could understand it
- write all the required information into a form ( in this case " it" refers to the form)
Glad you could make out the form.
- to come to terms , deal successfully with something , to manage something :
Glad you could deal successfully with it or
Glad you could manage it .
- detect with the senses, perceive .
Glad that you could discern it .