Extra Easy slimming world help!

I am new to slimming world and have a question which might sound a bit daft but here goes...

If a certain something that I want to eat is 500g and is syn free per 100g according to my app...does this mean the whole thing will be free or if I eat more than 100g do I then have to syn the amount I've gone over?

It's free no matter how much you eat but eat to your full.
It has syn values because say you are looking at potatoes they are free green and ee and synned on a red day so someone on a red day needs to be able to work out their syns