Open Question: I need to know..when printing my own postage for first class parcel on paypal?

it is default to not show how much postage was paid.I just leave it as it is.I pay for it as parcel as to not be machined just hand tossed because i am always shipping jewelry,beads earwires, jewelry supplies.Sometimes i forget to write fragile or handtoss.Will these items be processed thru a machine even though i paid parcel shipping even thought the label just says first class? Im just wondering if the post office is trained or has the equipment to read the barcode to know it is first class parcel to not machine it....