Summarize error with The express refers to multiple columns.

Anonymous 

If you are not doing any aggregation on Append1[Total].

Create a new column in the append table and use it?

Bucket =

Switch(true(),
Append1[Total]<=250,"0 to 250",
Append1[Total]<=500,"250 to 550",
Append1[Total]<=1000,"500 to 1000",
Append1[Total]<=2000,"1000 to 2000",
Append1[Total]<=2000,"2000 to 4000",
"Over 4000"
)

Anonymous 

You need to Create a calculated table not column or measure.