When does indices.fielddata.cache.size cause evictions?

I have
indices.fielddata.cache.size: 60% in my elasticsearch.yml.

Right now when I look /_nodes/stats/indices/fielddata?fields=* I see that indices.fielddata.memory_size_in_bytes has my nodes taking up more than 70% of the heap but my evictions is 0.

Shouldn't I be seeing evictions? and shouldn't the percentage be less than 60%?

Thanks,kick in?