A hundred in the Alps
The Alps lose about 100 people a year to avalanches, and that series is the solid part. The world figure of about 250 is an estimate.
The card says about 250 deaths a year, and the second line says the Alps are about 100. Those are different kinds of number. The Alpine one is a long count. The world one is an estimate that the avalanche literature repeats, and high mountain Asia is the part it probably misses.
The series
Combined fatality records for the European Alps, Austria through Slovenia, show about 100 deaths a year over recent decades. The mix has changed. Deaths in settlements and on transport corridors fell. Deaths among people out on uncontrolled snow, mostly recreation, became almost the whole of the toll. The annual total stayed near 100 anyway.
In the United States the Colorado Avalanche Information Center, which keeps the national accident record, reports an average of 27 deaths a winter over the last ten winters, and says fatal accidents are investigated closely enough to present that count with some certainty. Caught and buried, but alive, is a different matter: most non-fatal incidents are never reported.
The 250
Reviews of snow and ice avalanches cite a world estimate of about 250 deaths a year. Europe and North America are the well-counted share of that estimate. A review of high mountain Asia found hundreds of fatal events in the record that does exist, including years when a few catastrophes dominate the regional total. A smooth 250 cannot describe that, and it may be low. The card is allowed to say "about 250" only because the second line points at the Alps, which is the part a reader can actually check.
This card replaced falling icicles. Icicles were a round 100, usually hung on a report that Moscow saw about 10 deaths a year in the 1990s. Nobody had published the sum that turned 10 into 100. An avalanche burial at least has a register, even if the world line above it is still an estimate.
The glossary's natural disasters are earthquakes, floods and storms. A backcountry slab is not that line, which is why the avalanche stays here and the disaster line, on the unlisted toll, has no counter.