There are a number of reasons that there could be a difference between the balance available in Access WageEasy and in ESS.
Please check the following:
Leave in ESS will forecast to today's date. If you expand the leave, the Forecast balance, should match the total leave entitlements in Access WageEasy
Future dated leave applications. Any leave applications that are yet be processed in Access WageEasy will appear as either Not Yet Paid or Not Yet Approved field and will be taken away from the WageEasy balance to display the available balance in ESS.
Leave setup in ESS may not include pro rata calculation, go to Settings, Leave in ESS, check the settings for the Leave Type.
If there are problems Syncing Leave from WageEasy, this may cause the leave in ESS to not show correctly.