Answer:

The "Interval" times on the Monitor page should be 10 seconds or close to it, and the "Sample Times" should be less than 1 second

Here is an example where Foxhound is taking longer than normal to gather samples:

                         Heartbeat, 
                          Sample 
     Samples  Interval     Times  
  5:40:56 AM   14.3s    .1s / 13.2s
  5:40:42 AM   12.3s    .1s / 11.3s
  5:40:30 AM   15.9s    .1s / 14.9s

Have a look at the "SPs are OK:" field in the Monitor Status Area at the top of the Monitor page.

If it is showing SPs are OK: NNN or something other than SPs are OK: YYY, try to ensure that the Foxhound's three stored procedures for gathering performance statistics are installed on the target database; see Connecting to Target Databases.