Dimension is an embedded property of the `AWS::CloudWatch::Alarm` type. Dimensions are name/value pairs that can be associated with a CW metric. You can specify a maximum of 10 dimensions for a given metric.
`AWS::CloudWatch::Alarm`
The name of the dimension, from 1–255 characters in length. This dimension name must have been included when the metric was published.
The value for the dimension, from 1–255 characters in length.