Split sourcing rule not considered by Supply Plan while creating planned orders

• Plan type = constrained plan
• Item type = Buy item
• In plan options, ''Use alternate suppliers and source organizations'' is enabled under Constraints and Decision Rules.
• Item is not having any order modifiers ( min order qty, max order qty, FLM e.tc)
• Item is assigned to a Buy sourcing rule where 50% allocated to supplier1 and 50% to supplier2. Rank is 1 for both suppliers.

Ideally, demand quantity should be split equally between the suppliers while creating planned orders.

scenario: Created a forecast demand for quantity 22. It's being split to 2 planned orders, of quantity 1 (supplier1) and 21(supplier2) each. It's not split equally between the suppliers.