It means create an array starting at 0, incrementing by 25.5 each time, with a maximum value of 255.
Easiest way to see these things for yourself is just do it on command line on its own and see the result. Note that if the end value is not excactly on the increment from the start point then this value will not be included. It is a maximum end point for the array rather than an specific end point.
In this case it will be included:
0 25.5000 51.0000 76.5000 102.0000 127.5000 153.0000 178.5000 204.0000 229.5000 255.0000