How to enforce users to enter specific value in line item. E.g. I want user to enter only positve value in number line item. Line item should not accept any -ve number OR user should not enter value more then 100 etc.
You do not have validation at entering the value I guess but you can acheive this by below steps
1) Create an input line item
2) Create a line item with conditions if required
3) Create a line item with a formula which says if number is less than 0 then 0 else the number, if number is greater than 100 then 0 else the number
4) Have a conditional formula for line item created in step 1 with relation to line item created in step 3 (So if there is issue the cell colour turns red) so user knows something is wrong
5) Publish it to dashboard
6) Add text in the dashboard mentioning all the conditions applicable in order to number be a valid number