32bit I would of thought. The CPCs internal timer system, as used by KL TIME PLEASE (&BD0D), uses DEHL to return a four byte time count of the time elapsed, with D holding the most significant byte to L holding the least.
They don't have anything to do with the CPC really, the interface definition looks like:
property ID: Word read FID;
property Start: Int64 read FStart;
property Last: Int64 read FLast;
property Min: Int64 read FMin;
property Max: Int64 read FMax;
property Total: Int64 read FTotal;
property Count: Integer read FCount;
property Average: Double read GetAverage;