A method and device for estimating a number of distinct subscribers of a telecommunication network impacted by network issues include, for a plurality of N successive counting periods preceding a current time, steps of determining, for each counting period, an estimate of a number of different subscribers impacted by at least one network issue by implementing a probabilistic counter structure, and storing at least one elementary counter in association to said counting period, aggregating the elementary counters in a multi-level final counter structure, wherein each level of the final counter structure has an associated probabilistic counter structure, the aggregation comprising, for each elementary counter: computing, for at least one level of the multi-level final counter structure, an intersection between said elementary counter and the probabilistic counter structure associated to said level of the multi-level final counter structure, and updating the multi-level final counter structure based on the intersection computed.