What does the number 50 on the sign mean?

What does the number 50 on this traffic sign mean?

• A

  Maximum speed at which motor vehicles are allowed to run.

  According to the National Technical Regulation on Road Signs QCVN 41:2019, the "maximum speed allowed" sign (denoted as P.127) is used to indicate the maximum speed allowed for motor vehicles. This sign prohibits motor vehicles from traveling at a maximum speed exceeding the value indicated on the sign, except for priority vehicles.
  In this case, sign P.127 shows the number 50, so drivers are only allowed to drive at a maximum speed of 50km/h. Driving at a higher speed may result in a traffic violation.
  P.127 signs are often placed on roads passing through densely populated areas, heavy traffic, construction sites... where speed limits need to be applied.

• B

  Minimum speed at which motor vehicles are allowed to run.

Japanese

Source: https://vtcnews.vn/so-50-tren-bien-bao-co-y-nghia-gi-ar860617.html