Found the info on FTDNA's Alexander surname project:
R1b - Seven Brothers/Two Sisters (Ireland to Maryland) ALEXANDER Family [R-A848]
P312>Z290>L21>DF13>L1335>L1065>Z16325>S744>
S691>BY3146>A850>BY11749>A855>A848
STRs:
13 23 14 10 11-14 12 12 12 13 13 30 18 9-10 11 11 25 15 19 30 15-16-17-17 11 12 19-23 16 15 17 17 37-38 12 12 12 9 15-16 8 10 10 8 10 10 12 23-23 16 10 12 12 15 8 11 22 20 13 12 11 13 11 11 12 12 34 15 9 16 12 25 26 22 12 11 13 12 11 9 11 12 10 11 11 30 12 13 24 13 10 11 19 15 18 13 24 17 12 15 24 12 24 18 10 14 17 9 11 11