....And now the question - What is considered the correct reading for a given capacitor?
Yes, all readings are correct.
Just measurements at direct or alternating current or another frequency - most likely differ ...
For household crafts, the accuracy of the multimeter is quite satisfactory and I would like the tester to match them as much as possible.
Compared to you, I have little experience and knowledge in this area, and I will not even try to prove something and argue or philosophize - which is more correct, at what frequency .. at what current, etc. really correct value ...)))
And not many have professional devices.
In your photo, the readings of the multimeter and testers practically coincide, so I would like to achieve this.
Even with (-2%) correction, my tester falls short of the error range.
It measures resistors, transistors, diodes very accurately (less than 5% error), which is quite satisfactory even with this power supply and parts inside, but with capacitors the nuances are ...
Try to reduce the voltage of the stabilizer to 4.995-5.000v and power it from a stabilized source of 9-10v ...
I just thought that it is not very difficult to change one number in the file ... it would be quite suitable for my needs.
The option with replacing the power supply, I will take into account, if it really does not work out with recompilation, but this is as a last resort ...
Suddenly, you still have time and without replacing the parts you will be able to solve the problem