Read that book and hundreds of others. Truth is, you can equate recovery to a number or duration of taper days if you are consistent in what you track and always have valid HR and test numbers to go off of. That’s what tapering is all about. Taking just a long enough break or reducing intensities long enough for the recovery cycle to kick in and peak performances to rise for a specified event.
The thing is, it’s all about you. I can hammer a 850-1000 tss week one week, hit half of the previous weeks intensity Monday-Tuesday and taper Thursday- Saturday and hit peak performance on Sunday. But that May obliterate someone else. I’ve been doing it for a decade. It’s really the long lost art of feel. The old pros had to do it because they never had data to go off of. I’ve personally basically found my way back there starting from massive data banks and learning how to read the data into how I truly feel.
Only way that works is brutal honesty. Some days are great, some days are good but should have been better, some days are crap, some days you should have just recovered. You can’t lie to yourself if you want it to be right.