That config is gong to create a file with the hostname and date as the filename for each host every day.
Your file rotation settings will create a new file only after the existing file has reached 90 days old. The 'Total Number of log files" would limit the total number of files to be created that match the filename to 90. After 90 it would start to overwrite the oldest file. In this case it would do nothing since the filename will change every day without ever reaching the 90 day max age.
You could remove the date value from the filename. This would give you a file for each host that would rotate after reaching 90 days max age. Depending on what you are logging this file could be gigabytes in size, you may want to consider log rotation based on size(we use 250MB since most editors can handle that size file)
Once you had 90 files for an individual host the oldest file would be overwritten. In this case that would be after 8100 days. As bkyle suggested rather than use log rotation I would create a Schedule that would archive files that a greater than 90 days old.