If a page needs to be read from disk, it is counted as a physical read and a logical read. Logical I/O is always greater than or equal to physical I/O.
Logical I/O always reports 2K data pages. Physical reads and writes are reported in buffer-sized units. Multiple pages that are read in a single I/O operation are treated as a unit: they are read, written, and moved through the cache as a single buffer.