To create a list of 100 contacts you need to manually scroll using the horizontal scroll bar. Each scroll will load 10 contacts. 10 contacts are already loaded, so you need to scroll 9 times. Once done, please scroll up and select the contacts and it will show 100 subscribers selected. Click on bulk action and select "Add to Static list"
 
Once the contacts are added to the static list, please open the list, select all the contacts, click on bulk action and add a tag like "first100", so that you can identify them.
 
Please check the Gif that shows the selection of the first 100 contacts:
 
 
 
 
To select the next 100 contacts, please apply a filter "Tag is not first100" and it will list all the contacts excluding those 100 that were already added to the list. Now, scroll down again 9 times and scroll up to select the contacts and it will show 100 subscribers selected. Click on bulk action and select "Add to Static list"
 
Once the contacts are added to the static list, please open the list, select all the contacts, click on bulk action and add a tag like "second100", so that you can identify them.
 
Please check the Gif that shows the selection of the second 100 contacts: