here it works fine here using tdbf and TFloatField and TSmallInt, using Lazarus 0.9.31 r34164M FPC 2.7.1 i386-win32-win32/win64, what version of lazarus/fpc do you use? what kind of fields and database?
If you want to check in your current version, open the project at components/lazreport/samples/editor/ right click dbgrid and select columns, add a couple of columns and select PRICE and QTY fields, then set the display format one variant or your samples on each field and run it.