For me to count bacterial colonies I always use the Miles and Mizra method and it is true that it is outdated but very accurate for counting bacterial colonies.

If you do a google search for 'serial dilution and the standard plate count' you will get multiple sites with explanations and videos that demonstrate the procedures.

You may not have a homogenous suspension of bacterial cells in your inoculated tissue fluid.

I agree using Miles and Misra although very traditional is the recognised process. Ensure you start with a 0.5 McFarland turbidity suspension. Use calibrated pipettes and 20ul drops of suspensions. It has worked for decades Good Luck

i agree with Mairiead MacLennan