Is The Rated Current Of The Contacts For MY2 General-Purpose Relays 10 A As Written On The Relays Or 5 A As Written In The Datasheet?

The "10 A 250 VAC" written on the Relays is the UL/CSA rating and not the product specification. International ratings of this kind are based on under conditions specified for each standard. They are not the same as the ratings that satisfy conditions, such as the operating ambient temperature, outlined in the datasheet.

Do not use the Relays with currents exceeding 5 A.
Example: The UL standards specify 6,000 operations as the minimum test condition, whereas MY2 specifies 500,000 operations minimum.