Indextime extracted field requires wild card to search

[ips_mandar]

below is few sample of how my source filename look like-

source="\\abc.com\storage\Queue\Name1\abcdLogs\sample0008095200531.txt"
source="\\abc.com\storage\Queue\Name1\abcdLogs\sample0008096200531.txt"

Here Last 6 field before .txt represent Date. i.e. In above case 200531 is 31st May 2020.
I want to extract Id which comes before Date and after sample at indextime. and In Id if 0 are at left needs to be excluded(if present) so in above two cases my Id will be 8095 and 8096
Below is my transforms.conf -

[Id]
SOURCE_KEY = MetaData:Source
REGEX = sample0*([0-9A-Za-z]+)\d{6}.*txt
FORMAT = Id::$1
WRITE_META = true

fields.conf -

[Id]
INDEXED=true
INDEXED_VALUE=source::*<VALUE>*

Now when I search for ex. Id="8095" it won't return any results. but when I search Id="*8095" then it does return results. sometime I have to include wild card at start or at end to show results.
Why space is getting included at start or at end of Id? My doing anything wrong?
Thanks,

[s2_splunk]

Your RegeEx looks good, although I'd suggest replacing .*txt with \.*txt, i.e. match ".txt" literally.
In fields.conf, you may want to set INDEXED_VALUE=false, because you are creating a new indexed field named "Id", the value for which is NOT contained in the raw event text.
Let us know how it goes.