Short media diaries contain many zeros because many activities go unrecorded during the observation period. Log-ratio analysis of time allocation requires these zeros to be replaced with small positive values; as a result, all respondents who did not record an activity receive nearly the same value. We examined how such zero replacement affects classification in latent profile analysis and propose checks to perform before profiles are interpreted. Three-day diaries of 8,089 adults from the 2025 Korea Media Panel Survey were converted into nine-part time-use compositions. Gaming was not recorded by 88.9% of the respondents, and in every model with two to eight profiles and a covariance matrix held equal across profiles, respondents who recorded gaming and those who did not were classified into different profiles. Even when the replacement value equaled the minimum recording unit (5 min/day), the two-profile classification largely matched gaming recording status, and the two groups separated more sharply as the replacement value decreased, until the separation was complete. Before naming profiles, researchers should therefore check the proportion of respondents who did not record each activity and its replacement value, the same proportion within each profile, and the distribution of usage time among those who recorded the activity.

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