What did Mike write in Tina's birthday card

Mike writes the following:

Reach for the
stars!
Barry H

It's just a generic message, there's no real interesting information/easter egg here.

Reach for the stars! Barry H

This phase is actually a bit odd or ironic, because this is NOT common phrase seen on an adult birthday card for a women already in the workforce.

It's something that would be more common on a child's birthday card, someone graduating from high school or collage, and/or someone changing directions in life, as "reaching for the stars" is about embracing the future and hopefully finding what you are looking for. It's geared more towards a shift or change.

With that being said, you could apply this phrase in a few ways

1. Mike was being facetious towards Tina, because she's probably stuck at her job and has been in the workforce for a while.
2. He wrote it thinking about his granddaughter and her future, which is one reason why he has taken this job.
3. There is an irony in this phrase if you apply to Mike himself (like as if Mike was really writing it to himself), because he has just switched directions in his own life by taking this job and by being optimistic about his own future, when most viewers already know Mike's fate.
4. Better Call Saul is shifting this season, as it gets closer to Breaking Bad.