log.retention.bytes.per.topic does not trigger deletion

I tried using the following two retention properties

log.retention.bytes=3221225472
log.retention.bytes.per.topic=first_topic:1099511627776,second_topic:1099511627776

which I interpret to mean "by default, keep 3GB per topic partition, except
for first_topic and second_topic, which should retain 1TB each (across all
their partitions).

I've noticed that the data for first_topic and second_topic grow way beyond
1TB and no deletions occur. Is the syntax correct?

Thanks in advance,
Ben