They had supplied only 2 pieces for small size and 1 piece for large size as spares, not 4 pieces supplied as spares for each size as mentioned in the their email.
They supplied only 2 pieces as spares for small size and 1 piece as spare for large size, not 4 pieces supplied as spares for each size as mentioned in the their email.
The second is closer but you are missing the articles. ] and one spare for the large size, not the four spares for each size, which was what their email promised.
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The second is closer but you are missing the articles. I would say:
They only supplied two spares for the small size [of what?] and one spare for the large size, not the four spares for each size, which was what their email promised.