Texas State Alpha Delta Pi
The additional Greek letters you are seeing are individual chapter names.
Alpha Delta Pi names chapters in order of founding - 1st: Alpha, 2nd: Beta, 3rd: Gamma, 4th: Delta, etc. Once they run through the Greek alphabet, they start adding more letters in Greek alphabetical order -
Alpha | Beta | Gamma | Delta | Epsilon | Zeta | Eta | Theta | Iota | Kappa | Lambda | Mu | Nu | Xi | Omicron | Pi | Rho | Sigma | Tau | Upsilon | Pi | Chi | Psi | Omega | Alpha Alpha to Alpha Omega | Beta Alpha to Beta Omega | Gamma Alpha to Gamma Omega | Delta Alpha to Delta Omega | Epsilon Alpha to Epsilon Omega | Zeta Alpha to Zeta Omega | Theta Alpha to Theta Tau. (Theta Tau is the newest chapter of Alpha Delta Pi, installed April 2014.)
Some chapters may no longer be active, but the chapter name is retained.
Visiting where it all began in 1851 at Wesleyan College in Macon, GA
ADPi Summer <>
I was blessed to meet a fellow sister on the boat from the Zeta Omega chapter!