The Width formatting option for numeric fields (see Numeric data type) determines how large a number the field will accept. The options are as follows:
Byte The field will accept numbers from 0 to 255
Integer The field will accept numbers from -32,768 to 32,767
Long The field will accept numbers from -2,147,483,648 to 2,147,483,647
Currency The field will accept standard currency formats, including decimal places and currency symbols
Single The field will accept negative numbers from -3.402823E38 to -1.401298-E45 and positive numbers from 1.401298E-45 to 3.402823E38
Double The field will accept negative numbers from -1.79769313486231E308 to -4.94065645841247E-324 and positive numbers from 1.79769313486231E308 to 4.94065645841247E-324
Note that Double is the default width for all new Numeric fields. If you wish to enter numbers that that refer to another table's primary key where the primary key is an Incremental field, use the Long format.