How to calculate Redis memory usage

I have an Elasticache Redis instance on AWS and I want to monitor its memory usage and send alerts when it exceeds a certain threshold. The Redis info command provides several memory-related metrics, including

used_memory:3651689760

used_memory_human:3.40G

used_memory_rss:3684122624

used_memory_rss_human:3.43G

used_memory_peak:3704319760

used_memory_peak_human:3.45G

used_memory_peak_perc:98.58%

maxmemory:20975001908

maxmemory_human:19.53G

I would like to calculate the total memory usage of Redis based on these metrics and send an alert when the usage exceeds a specific percentage.

Can anyone provide guidance on how to calculate Redis memory usage based on the info command output?

Thank you in advance for your help!