HI angel77,
If someone post Gb7 that means play Gb Bb Db Fb/E. That just means to play Gb major which is Gb Bb DB and add a flattened 7 which would be Fb/E. Let me give you another example, say if someone says GbM7, that means to play Gb major and add the 7th note which is F. The Gbmaj scale is
Gb Ab Bb Cb/B Db Eb F Gb
1 2 3 4 5 6 7 1
So the 1 3 & 5 makes up the major chord which is Gb Bb & Db then you just add on the seven or flatten it depending on what it says to do. Hope this helps you.
God Bless