If you are seeing a larger total than the sum of it's parts, e.g. the total number of books (144) is higher than it should be (29):

Apologies, this is a known bug in Discover which incorrectly includes extra book records. To correct the number and remove the incorrect records, just select any of the eBook/Print Book/Thesis options and Discover correctly re-calculates the number:

If you subsequently re-select all options you will also see the correct total and records:

Our suppliers are aware and will fix this bug soon.