Your email alert will change when you change the number of patents in your workspace but this change will only occur for the email alert after your next one. So the next email alert you receive will still consider the previous number of documents you had.
For example, if you set up a weekly email alert which will send you an email every Sunday then if you change the number of patents in your workspace on any other day of the week, then on the Sunday after this the email alert will still be considering the previous number of patents but on the Sunday after that the new number of patents will be considered for the email alert.