Timing belt model codes look cryptic but follow simple rules. There are two main conventions: imperial (XL, L, H) and metric (HTD 8M, AT10, T10).
Imperial: 200XL037 means 200 teeth, XL profile, 0.37 inch width. 320H050 means 320 teeth, H profile, 0.50 inch width. The number before the profile is always teeth, the number after is always width in inches.
Metric: 720-8M-30 means 720 mm pitch length, HTD 8M profile, 30 mm width. AT10-1500-25 means AT profile, 10 mm pitch, 1500 mm pitch length, 25 mm width. Different metric prefixes order the fields differently, so always check the spec sheet for the exact convention.