Value disk in headline email alerts

now when i set in alert description {{ $value }} i get value=86.02566755352139 this is percentage used Disk. But when i write to Name of alert Rule this tag dont work. I have Template for email.subject where i have this

{{ define “email.subject” }}
{{ if eq .Status “firing” }}[Pozor!]{{ else }}[OK]{{ end }}: {{ .GroupLabels.grafana_folder }} : {{ .CommonLabels.alertname }} {{ .CommonLabels.rulename }}
{{ end }}

This give me in my langueage
[Pozor!]: (New grafana) : Nedostatek místa na Disku F {{ $value }}
this mean Alert! (New Grafana) : You havent space on disk F and now i need value of currently state from disk.

Grafana doesnt support this now or i doing somethink wrong?