Can't edit alarm conditional trigger "condition length" values?

[TedH256]

I'd like to configure a "datastore usage on disk" trigger (which is a conditional trigger) but the "condition length" field for either warning or alert -- don't let me pick or type any values.

What am I missing?

vCenter standard 5.1, hosts licensed with Enterprise

[rvirene]

It depends on the alarm - I have some that let me set the condition length and some that do not.

Datastore Usage on Disk does not and Host CPU usage does for example.