I believe it's 20 business days, IG
I think that on the OTC, the "D" remains on the symbol for 20 business days, not calendar days.
For LIBE's last RS in 2016, the "D" was added on 9/8/16 and removed on 10/5/16 which, counting the eighth, was 20 business days.
Depending on whether or not they count this week's MLK holiday as a business day, the "D" should be removed on Feb 6 or 7.