Safe Puzzle Solution
Numbers on the note are the key, for example there is word “gloomy” with the number 6, next one is “and” with number 1 etc. It basically tells you that you are supposed to count words in each line.
Once you realize some words from the voicemail are capitalized, you should know the combination, because you can find them on the note. (week, lying, missing, person) That is why the answer is 2443.
P.S. One last thing about the 6152 from the note – this combination triggers 2 additional jumpscares if you try to open the safe with it.