Unfortunately we do not have an official equation but it can be estimated since it looks to be linear to the Log of the delay value so the following formula could be used assuming a 20kOhm increase per decade.
R_dly = 20kLog(t_dly) + 108k,
eg. t_dly = 15ms then this would approximate R_dly = 71.5kOhm
This holds relatively accurately within the range of table 3 values.