Set custom content that will appear on the tooltip
Use special variables:
${__y_label} name of the time series (alias or legend in the query editor).
${__y_label_trim} trimmed name of the time series (alias or legend in the query editor).
${__y_label_N} partial name of the time series (alias or legend in the query editor), only valid when custom y-label is enabled.
${__url_time_range} refers to graph range in the form of 'from=...&to=...'.
${__value} refers to current bucket value or max value if multiple values mode is on.
${__value_N} refers to Nth value in current bucket. Value indexes are started from 0. For instance,
${__value_1} refers to second value.
${__value_date} refers to __value formatted as date.
${__value_N_date} refers to Nth value in current bucket formatted as date.