Official communications and media news in Greece about the COVID-19 pandemic very often involve a multitude of numerical concepts and mathematical relationships, which are presented in different forms and in various contexts. This paper reports selected findings of a survey among adults, which had two aims. First, to investigate their subjective assessments concerning the difficulties encountered in reading and understanding such numerical information, embedded in texts and presented by infographics and time-series graphs. And second, to investigate their assessments of the usefulness of such numerical information, presented in visual forms. A convenience sample of 310 adults responded to an online questionnaire. The main conclusion from the analysis of these data is that a considerable number of the participants, although relatively highly educated, assess themselves as having difficulties in reading and understanding numerical information concerning COVID-19. Namely, about 9% report difficulties with information included in textual forms, while regarding visual presentations the percentage ranges from 10% to 35%. Yet more than half of the adults surveyed assess the presentation of numerical information in visual forms as useful for comprehension. Furthermore, the distributions by gender, education, and age of participants' answers to our questionnaire generally show no substantial differences among them. These findings advise caution regarding communications or announcements that involve even simple numerical concepts and mathematical relationships concerning COVID-19 and health issues.