I think the advice was to discuss with your GP who has access to all your results.
If liver disease can be excluded by liver function tests and/or scans, and your blood tests do not show any sign of haemolytic anaemia (breaking down of red blood cells) then the most likely cause of a borderline high bilirubin would be something like Gilbert's syndrome...
As i recall ,it has been mentioned following previous number of tests in the past , but the GP has never said to me that it needed investigating further .
I'll ask to have it investigated further .
Your GP may or may not want to investigate - he/she may have information already to decide whether this is necessary. If the bilirubin level was 41 last year and 28 now it's not going up which is reassuring. It's worth asking though.
The kidney function figures look all right, the GFR is age dependent - it reduces as we get older.
An average 20 year old might have a GFR of 120 ml/min, an average 70 year old would have a GFR of 70 ml/min. In practice any thing above 60 ml/min is considered to be OK.