Usage: 2 forms in 2 verses
Form Translated As     In Verse(s)
κάτεργον upkeep LXX.Exod.30.16
κάτεργα upkeep LXX.Exod.35.21

Liddell-Scott-Jones

κάτεργος (katergos) upkeep G:N-N

κάτεργος, ον,

worked, cultivated, χώρα [Refs 4th c.BC+]

__II κάτεργον, τό, wages, [Refs 3rd c.BC+], etc.; labour-costs, τὸ εἰς τὴν πλίνθον κ. γεινόμενον [Refs 3rd c.BC+]; εἰς κ. τῆς σκηνῆς for the service of the tabernacle, [LXX]

LSJ Scripture Refs: LXX.Exod.30.16