Significant attention has been paid to the use of ICT by teachers, especially during the COVID-19 health crisis. This usage has mostly been captured through self-reported survey measurements. Learning analytics can complement such findings, by using log data to document precisely how long teachers use ICT, and what ICT behaviors they perform online. Using log data of 800 teachers, the present study documents their use of ICT in mathematics on a digital learning platform used across Luxembourg during COVID-19 remote education. Our findings confirm the large differences between teachers' use of ICT found in previous research, measured here through the time spent active on the platform. The types of ICT behaviors teachers engage with online, measured via the SAMR model, explain most of this variation. Specifically, more time on the platform is associated with activities that create a meaningful learning experience, and redefined tasks that could engage students as active learners. Experience with the technology, and participation in incentive events and teacher training, explain another significant part of this variation.