A stream’s weight value is used to determine traffic distribution – by percentage – when your campaign has more than one Stream added.
When you create multiple Streams, they are automatically assigned a default weight of 100.
This is to ensure that your traffic is distributed at an even ratio for a new campaign.
Note: You can edit your Stream’s weight at any time to redistribute traffic at an optimal ratio.
It can be done once the performance of a Path has been accurately measured following the campaign's "testing" period.
For example, if one lander is doing better (higher CTR %) than another within the same campaign, you can increase the path weight of the best performing lander to distribute traffic at a higher ratio to the better performing LP.