Running function on Sonata Admin List field - symfony

Question

In my application, backend users can segment frontend members through criteria like age, gender etc. These criteria are saved in a class called Segment.
AppBundle\Entity\Segment:
type: entity
table: segments
fields:
id:
id: true
type: integer
generator:
strategy: IDENTITY
name:
type: string
length: 300
created_at:
type: datetime
updated_at:
type: datetime
nullable: true
oneToMany:
parameters:
targetEntity: SegmentFilter
mappedBy: segment
cascade: [persist]
manyToOne:
owner:
targetEntity: Application\Sonata\UserBundle\Entity\User
inversedBy: null
joinColumn:
created_by:
referencedColumnName: id
The SegmentFilter class holds the parameters for filtering the members eg. criteria can be 'age', 'description' can be null but its for clarity purposes for whoever is reading the criteria and finally value can be '>= 30'
AppBundle\Entity\SegmentFilter:
type: entity
table: segment_filters
fields:
id:
id: true
type: integer
generator:
strategy: IDENTITY
criteria:
type: string
length: 50
description:
type: string
length: 300
value:
type: string
length: 300
manyToOne:
segment:
targetEntity: Segment
inversedBy: paramemters
joinColumn:
segmentation_id:
referencedColumnName: id
Here's the member's class to be segmented based on the parameters defined for each segment:
AppBundle\Entity\Member:
type: entity
table: members
fields:
id:
id: true
type: integer
generator:
strategy: IDENTITY
first_name:
type: string
length: 20
last_name:
type: string
length: 20
mobile:
type: string
length: 11
address:
type: string
length: 255
zip:
type: string
length: 6
town:
type: string
length: 25
email:
type: string
length: 50
dob:
type: date
In the list of segments, I would like to add an extra field that shows how many members currently fall in each segment created. How would I go about this?