mitPradikat identified how the original confusion probably came about due to differences in how Grand and Premier are used in the Bordeaux and Burgundy classification systems.
The 1855 Bordeaux Medoc classification placed individual estate wines into 5 Grand Cru Classe with Premier Grand Cru Classe [First Growths] being the highest designation, Deuxieme [Second Growths] next and so on down to Cinquieme or 5th Growths - thereby implying that 'Premier' was somehow above 'Grand'.
Burgundy's classification relates not to separately owned estates but to land which was usually shared by many owners/producers - although there are a few single owner Monopoles. In that classification of land [or terroir] the top designation for vineyards is Grand Cru followed by Premier Cru and down through lower designations to simple Bourgogne.
So in Burgundy, Grand Cru is the top designation although, as with the Bordeaux classification, many experts feel that individual producers make wine that is often better than [or in some cases worse than] their classification or simply better or worse than others on land classified at the same level.
For example, some 5th Growths in Bordeaux are considered today to be as good as some original 2nd Growths and in Burgundy some Premier Cru wines from some producers are considered to as good as Grand Crus from others. And that some Premier Cru land [as distinct from producer] should be re-classified as Grand Cru and vice versa.
Others have already explained the further differences in Bordeaux e.g. St. Emilion, Alsace, Champagne et al but as mitPradikat suggested the original question came about due to an apparent [but not actual] 'contradiction' between the use of the words ‘Grand’ and ‘Premier’ in Bordeaux as compared with the Burgundy classification.