Nested preload limit - set to 5 but it's returning 3

Hello there im working on pagination on my query

first lets see my query

query
    |> join(:left, [o], op in OrderProduct, as: :order_product, on: o.id == op.order_id)
    |> join(:left, [o, op], p in Product, as: :product, on: op.product_id == p.id)
    |> preload(
         [order_product: op, product: p],
         [
           :order_type,
           :merchant,
           :customer,
           :payment_method,
           order_product: {
             op,
             product: p
           },
         ]
       )

is valid query and its working, after giving it limit the result mess up

what i mean by mess up is i set the limit 5 but it return 3
i thought it was my query but after hour debugging i realize if i remove nested preload to be this

  query
    |> join(:left, [o], op in OrderProduct, as: :order_product, on: o.id == op.order_id)
    |> join(:left, [o, op], p in Product, as: :product, on: op.product_id == p.id)
    |> preload(
         [order_product: op, product: p],
         [
           :order_type,
           :merchant,
           :customer,
           :payment_method,
#           order_product: {
#             op,
#             product: p
#           },
         ]

it working and find any idea what is going here ??