Top and Bottom filter requires you to specify an integer value, and there is no native option to leave it blank and display all values. However, you can achieve the desired behavior with a workaround.
Workaround: Use a Parameter-Controlled Filter
Create a parameter (Ex: TopBottomCount) of type Integer.
Set the default value to a high number, such as 1000, to cover most scenarios.
Add a control for the TopBottomCount parameter in your analysis/dashboard.
Add a Top and Bottom Filter to your visual.
In the filter settings, use the TopBottomCount parameter as the value for the filter.