Database version : 19c
OEM version: 13c Release 4 Update 8
For the tablespace full OEM alerting, I currently use the standard % based thresholds : 85% as the warning threshold and 97% as critical threshold.
In my shop, I have DBs which have large tablepaces. For example, I have a tablespace which is 4TB in size.
When I add a 32GB datafile to a 4TB tablespace, it does not even reduce the utilization by 1%.
So, for large tablespaces, instead of the warning/critical alerts being sent out based on % of space exceeding a threshold, I want the warning/critical alerts to be sent out only when remaining free space falls below a certain threshold. i.e, I want to use the setting highlighted in red box below.

My question:
What should be the cut-off size for a large tablespace for me to start using the alerts based on "remaining free space falls below a certain threshold" ?
For example, can I start using this threshold, when a tablespace grows beyond 1 TB ? What is the convention you guys follow ?