Every SQL Server database has two type of files added; Data file and Log file and same goes for system databases as well. You can change the size of User-Defined Databases when they are created but not when System Databases are getting created by the Installation. However, with SQL Server 2016, we have a new page in the installation wizard that allows you to make some changes to the Tempdb.
As you see, you can change the number of files required for the tempdb, initial size of them and the increment for Auto Growth. Although file size can be changed as you want, it does not allow to change the Log Initial Size beyond 1,024 MB. If you set a larger value, it automatically sets to 1,024MB.
This does not mean that you can set a larger value to tempdb log file. Once the installation is done, you can change it later with the size you need. I assume that the reason for not allowing to set the size larger than 1,024MB during the installation is for saving the overall time for the installation.