OMS (SelluSeller): This could be due to pre-booking promotion set in OMS (SelluSeller) for the product SKU where stock is inflated in the catalogue page in OMS (SelluSeller) and Marketplace.
Wareo: There could be the possibility of stock addition of 1 piece via stock adjustment performed.
We hope the details above were helpful for you. Please feel free to share with us if require further assistance and will be happy to take it up.