Update: The account has deleted the tweet, but considering how much work went into the video that announced it, it probably just went up early. It is likely the dates are the same as they were outlined below.
The original story is as follows:
Bandai Namco has announced an upcoming network test for Soulcalibur VI ahead of the game's release next month for Xbox One and PlayStation 4.
Warriors, prepare yourself for online battles on PS4 & X1! You are invited to help us test our online network for SOULCALIBUR VI. Login and play RANKED MATCH mode!
— SOULCALIBUR (@soulcalibur) September 21, 2018
Download the #SOULCALIBUR VI network test on September 27th and draw your weapons on September 28th at 8AM PDT. pic.twitter.com/3PqXdXBGb2
The beta runs from 8:00 a.m. September 28 PDT through 8:00 p.m. PDT September 30. There will be 15 characters playable on 9 stages. The client can be downloaded on September 27, one day ahead of the beta start time.
While Soulcalibur VI is releasing on PC, as well, the beta has only been announced for Xbox One and PS4. The game will release on all three, however, on October 19.