Since anaerobic work capacity is so small it is extremely sensitive to where you make the cutoff from aerobic and it's pretty much entirely pointless to consider in isolation from power estimates that themselves have significant uncertainty.
If you do a 7 minute effort at 500W and you set the cutoff at 450W, that comes out to 21kJ of anaerobic work. If you set the cutoff at 440W (10W or 2% of 500) you get 25.2kJ or 20% more. So a small uncertainty in wattage and cutoff is translated into a "useless" uncertainty for anaerobic work.
If you do a 7 minute effort at 500W and you set the cutoff at 450W, that comes out to 21kJ of anaerobic work. If you set the cutoff at 440W (10W or 2% of 500) you get 25.2kJ or 20% more. So a small uncertainty in wattage and cutoff is translated into a "useless" uncertainty for anaerobic work.