Kalimera! Often in old equipment that has been repaired, one finds newer components. As Maarten says, availability plays a part as more modern parts have different values from older ones, because of changes in the spacing between values in each decade -
the "E Series of Preferred Numbers".
In this case, especially small changes as between 50µF and 47µF, use the next available modern value. In other cases, it can make very little difference depending on where in the circuit the capacitor is used. In an RC filter or in a valve rectified power supply, there will be a requirement for certain values that can be obtained by calculation.
Remember that most capacitors have quite poor value regulation, so tolerances of +/-20% is normal, with variances that can be even greater depending on frequency and temperature.
That plan you attached is very small so it's hard to see it. Try exporting the file rather than taking a screenshot, or if the forum compression makes it too small I've had success linking files from Dropbox or similar.