The massive development chart at digitaltruth says for asa=125 and dilution=1+50, the time is 15 minutes. I'm pretty sure that I used their 1+25 dilution figure for time and the results were good, so I'd go with their 15 minutes
Sounds about right. AGFA shoots for a higher contrast than most of us would use for scenic photography. They like CI to be 0.65. We are more inclined toward 0.56. Rodinal at 1+50 does not build contrast very rapidly after about 10 minutes, so the difference between 15 and 16 minutes may hardly be noticable.