Why am I seeing a long number at the end of the collector name on a newly installed collector?

A 13 digit number after the collector name is the epoch timestamp added when the collector was first installed and registered. Collector names within an account must be unique so this number may be applied to a Collector name if another Collector with the same given name already exists within your Sumo Logic account. 

If you wish to automatically delete a previous Collector with the same given name and have a new Collector installed in its place, you can use the clobber flag available with the installation parameters of the Collector. This parameter should be used with extreme caution. Once a Collector is deleted from the service it cannot be recovered and any Source details will be lost.