Creating health.d config cross referencing two charts as calc

General
1

I have a chart created that exposes the nginx workers and it works just fine. However I wanted to create an alert that cross references two charts in the calculation

Here is my alert -

template: nginx_connection_alert
      on: nginx.connections
   every: 5s
    calc: $active * 100 / ${chart:nginx_worker_connections.worker_connections:max_connections}
    warn: $this > 0.1
    crit: $this > 0.2
    info: Nginx connection usage: $this% (Active: $active, Worker Limit: ${chart:nginx_worker_connections.worker_connections:max_connections})
      to: sysadmin

Here is the created chart.

localhost:19999/api/v1/data?chart=nginx_worker_connections.worker_connections
{
        "labels":["time","max_connections"],
        "data":[
            [1753475078,1024],
            [1753475077,1024],

I’ve set the threshold too low just for testing. Normally it will only have 1 to 2 active nginx connections
Calculation does not seem to work. What am missing?