So you want to store 2 values in 1 spot? Your answer is tables.
local weapons = {}
tabel.insert ( Cart.weapons, { weaponid, weaponid } )
This will appear like this.
Cart.weapons = { { weaponid, weaponid }, { weaponid, weaponid }, { weaponid, weaponid } }
OR if you meant insert more values, just call table.insert again.