Autofilter help please

[Jack Sheet]

Cell M228 contains a text string with value
BR1741

Cell L228 contains a formula
=IF(ISBLANK($M228),"",VALUE(MID($M228,3,4)))
and displays the text string
1741
(as predicted)

Both cells are included in an autofilter range.

If I autofilter column M on condition
Contains 1741
then row 228 is displayed (as desired)

If I autofilter column L on condition
Contains 1741
then row 228 is hidden (not desired)

Any idea what is going wrong?

Thanks

 

[Jack Sheet]

Duh, forget that. I see it