nobody knows?

It's OK, electrolytics are usually rated with a 20% tolerance and that is taken into account by the engineers who design the circuits. It will be fine, especially if you have chosen a quality brand and the specs closely match the ones you want to replace.

Generally motherboard capacitors are closer to their rated value when new and drift quite a bit once used which is where the 20% tolerance comes from.

The renowned capacitor manufacturers like Rubycon, Panasonic, Nichicon and Nippon Chemicon normally guarantee a tolerance of +/- 20% or better.
Measurments have shown they mostly stay inside an interval of +/- 5% - 10% easily.

Suppliers of cheap caps often allow -20% and less because lower capacity means lower costs.

If a new capacitor from a trusted manufacturer shows a capacity below the tolerance interval this can also happen due to a long stocking period. Electrolytics tend to "de-format" when they are not used. In this case the nominal capacity will recover, after the capacitor has been reformatted by connecting it to DC for some time (days).