assigning a Data Validation contraint as in the attached screenshot causes an error when e.g. the German or Polish browser locale is used.
(the error didn't happen when using an English locale - assuming a different number format causes this)

this error can be reproduced on the demo side directly: http://zssdemo.zkoss.org/zssdemo/excel_like

SEVERE:
org.zkoss.zss.model.InvalidFormulaException: Unused input [.0] after attempting to parse the formula [1.0]
at org.zkoss.zss.model.impl.DataValidationImpl.parseFormula(DataValidationImpl.java:574)
at org.zkoss.zss.model.impl.DataValidationImpl.setEscapedFormulas(DataValidationImpl.java:595)
at org.zkoss.zss.model.impl.DataValidationImpl.setFormulas(DataValidationImpl.java:584)
at org.zkoss.zss.range.impl.RangeImpl.setValidaitonInLock(RangeImpl.java:2187)
at org.zkoss.zss.range.impl.RangeImpl.access$3100(RangeImpl.java:104)
at org.zkoss.zss.range.impl.RangeImpl$61.invoke(RangeImpl.java:2146)
at org.zkoss.zss.model.util.ReadWriteTask.doInWriteLock(ReadWriteTask.java:43)
at org.zkoss.zss.range.impl.RangeImpl.setValidation(RangeImpl.java:2156)
at org.zkoss.zss.api.impl.RangeImpl.setValidation(RangeImpl.java:786)
at org.zkoss.zssex.ui.impl.undo.DataValidationAction.doAction(DataValidationAction.java:143)
at org.zkoss.zssex.ui.impl.UndoableActionManagerImpl.doAction(UndoableActionManagerImpl.java:50)
at org.zkoss.zssex.ui.impl.ua.DataValidationHandler$2.onEvent(DataValidationHandler.java:165)
at org.zkoss.zssex.ui.impl.ua.DataValidationHandler$2.onEvent(DataValidationHandler.java:141)
at org.zkoss.zssex.ui.dialog.impl.DialogCtrlBase$1.onEvent(DialogCtrlBase.java:59)
at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:2758)