Unable to append the %s to --left-axis-format

[Nakilon]

When the GAUGE value is 500, 600, it displays correctly with this:

  "--left-axis-format", "%.0lf",

But when there are higher values, like 5000, 6000, it displays as just "5","6". I suppose this is what the %s is for and docs https://oss.oetiker.ch/rrdtool/doc/rrdgraph_graph.en.html include an example of using them together like this: %lf%s. However when I do the:

  "--left-axis-format", "%.0lf%s",

I get the error:

invalid format string '%.0lf%s' (should match '^(?:[^%]+|%%)*%[-+ 0#]?[0-9]*(?:[.][0-9]+)?l[eEfFgG](?:[^%]+|%%)*$') (RRDError)