How to have tsvb Gauge visualization showing the last value

When dashboarding netdata host metrics , using tsvb line graps, I can have the avg by 30s graphed which is more or less the last value I'm interested in.
(netdata samples 3000 metrics every sec, logstash http poller samples it in 30sec)
However when I have the same metric:disk_space._data00.avail for the gage, I either have 0 (30s) or 4,163,650 (1min).

In Discover: metric:disk_space._data00.avail value: 673.223
Any ideas?

In Kibana-Level Up these aggregations were mostly counts.