We would like to utilize the MaxFileInputsCount

//RadAsync Upload

 <telerik:RadAsyncUploadID ID="ruAttachments" runat="server" Width="100px" MaxFileInputsCount="3" TemporaryFileExpiration="20"   
                                                                        OnClientValidationFailed="ValidationFailed" OnClientFileUploadRemoved="ValidationError">
 </telerik:RadAsyncUploadID>

and the TemporaryFileExpiration configurations

//RadAsync Upload

<telerik:RadAsyncUploadID="ruAttachments" runat="server" Width="100px" TemporaryFileExpiration="00:20:00" 
                                                                        OnClientValidationFailed="ValidationFailed" OnClientFileUploadRemoved="ValidationError">
</telerik:RadAsyncUpload>

that are available in the Telerik UI for ASP.NET Ajax in the Telerik UI for ASP.NET Core.