Add totals at the end of a filtered list, but with conditions?

Hello Everyone. I have tried looking through the other posts, but cant find this specific query, and if something is close to my query, I'm not able to change it to make it work for me, sorry.

Anyway. I'm trying to filter how many cables of a certain type are in each electrical control panel.
I have a Spreadsheet that has cable number/codes in column b, and electrical control panel names in column d, but when i apply the filters in column d (by electrical panel type) the totals at the bottom of column b don't change. Additionally, when i filter by electrical panel it leaves several types of cable in column b and it its these totals I'm trying to filter. The codes for the cables change (depending on manufacturer) but its the amount of cores in the cable I'm trying to show. eg: on cable code is EICCXH24ANE-xxx (the "24" shows the core numbers) and the "24" is the constant i'm trying to dd up, so i've used =COUNTIF(B2:B231,"*24*") which works fine, but doesn't change when filtered.
im sorry this is quite a long one, just hoping someone out there is much more familiar with what im doing wrong! I only have this sheet to do now, but over the next 6 months ill have another 20 to complete!
ive attached a basic version of the sheet im trying to work on, and any help will be very very much appreciated.