I think what he means is, from the point of the driver driving from the 50 to the 60 area:
You drive fifty, then you pass a sign pointed away from you (towards oncomming traffic) saying 50.
65m further, you pass a sign pointed at you saying 60.
In that case I would say the speedlimit is just different for that 65m stretch of road, based on the direction of travel.
The speedlimit changes at the 50 sign if driving from 60 to 50, and at the 60 sign if driving from 50 to 60.
I think what he means is, from the point of the driver driving from the 50 to the 60 area:
You drive fifty, then you pass a sign pointed away from you (towards oncomming traffic) saying 50. 65m further, you pass a sign pointed at you saying 60.
In that case I would say the speedlimit is just different for that 65m stretch of road, based on the direction of travel. The speedlimit changes at the 50 sign if driving from 60 to 50, and at the 60 sign if driving from 50 to 60.