Round to nearest in table

I have a table like this:

image.png743×481 10.5 KB

#4 (per stuk) is the total amount of the part (raw material) divided by the quantity to make for this order. Works fine, but sometimes I get a output like 410.111111111111 - and I would like to round that to 410.1

These 2 fields (parts_booked & quantity) are a string by default, and I tried to change it to number like this:

image.png435×611 13.7 KB

But as soon as I save that, nothing changes in the field expression, it stays: parts_booked / quantity. When I reopen with the magic wand, the value type is back to string again.

Also I have tried adding .toNumber() to the field expression, but then it gives an empty table column.