Values and the golden rule
Rough values: chariot 9, cannon and horse about 4.5 each, advisors, elephants and soldiers 1-2, and a soldier doubles once it crosses. The golden rule of exchanges (兑子): when you are AHEAD in material, trade pieces — every even swap shrinks the board and makes your extra unit louder. Red here is up a crossed soldier, so offering the chariots is exactly right: whatever Black recaptures with, the endgame that follows plays itself in Red's favour. Make the offer.