If the pattern says to cut 4 7/8" squares it will finish as 4" square
(with no margin of error).
When I make HST's I just round off to the next digit. In this case I
would cut 5" square. Sew 1/4" on each side of the diagonal, cut,
press and trim to 4.5" square. After sewing it should finish at 4" square.
If you want to make 8 HST's at a time then you just double the measurement.
Cut your square 10" square. There are charts that are more skimpy or more
generous. Try different ones and see what you like.
I agree with Bearisgray. Avoid those bias edges.
You can check here for a good tutorial and a chart.
If you only need 4 HST's then you do half of it. You will start
with a rectangle that's 5" x 10". But I would suggest you start
with 8 first to know how this works.
https://www.generations-quilt-patter....html#Download