add blob to basics documentation about negative shift
add blob to basics documentation about negative shift

Signed-off-by: schou <5bd3ee1c8682c61c1c753c983f60e358e2ada344@users.noreply.github.com>

GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,keegancsmith/prometheus,prometheus/prometheus,alileza/prometheus,prometheus/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,keegancsmith/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,keegancsmith/prometheus,alileza/prometheus,alileza/prometheus,prometheus/prometheus