From Teradata documentation, the definitions of these ResUsageSpma columns are:

FilePres Total number of times a cylinder is loaded.

FilePreReads Number of times a cylinder is loaded.

which look similar, but I observed on our lab's Teradata and found quite different values with an observation that:
FilePres = 2 x FilePreReads (approx.)

I also looked into KA but couldn't find any explanation. Please respond if you know the meaning of these fields.