Search function in ContentExplorer

We have two files in the same folder.

'3BA12193-65E5-4E6D-9A1E-***number removed for privacy***6B.jpeg' and

'FB842434-3FB4-4542-9730-5D83A01F80E8.jpeg'

When we input '3' in the search field, there is no file in the search result.

Is it a issue for the explorer, or is there any rule for the search API?