Before you replied I already change it. Could I just confirm (just in case there would be potential issues) the following:
(1) in eCart object instead of Number I used Integer (would this be a problem, what is the difference between those 2 options)
(2) in my database I ended up using Float for weight fields and Float for Sizes (because sizes will have a 2 decimal point value).
For weight even though I used Float would this cause any issues? Yes the delivery companies provide whole numbers. But also the shopping basket could have a weight of a 2 decimal value so I figured just to keep them as Floats. Any downsides?