To calculate the seasonal $($daily$)$ indices, we first need to calculate the average number of meals served each day of the week over the four weeks. Then, we calculate the overall average of meals served per day. The seasonal index for each day of the week is then calculated by dividing the average for that day by the overall average.

Let's start by calculating the average number of meals served each day of the week:

Sunday: $(40+35+39+43)/4=39\mathrm{.}25$

Monday: $(54+55+51+59)/4=54\mathrm{.}75$

Tuesday: $(61+60+65+64)/4=62\mathrm{.}5$

Wednesday: $(72+77+78+69)/4=74$

Thursday: $(89+80+81+79)/4=82\mathrm{.}25$

Friday: $(91+90+99+95)/4=93\mathrm{.}75$

Saturday: $(80+82+81+83)/4=81\mathrm{.}5$

Next, we calculate the overall average of meals served per day. We add up all the daily averages and divide by $7($the number of days in a week$)$:

Overall average $=(39\mathrm{.}25+54\mathrm{.}75+62\mathrm{.}5+74+82\mathrm{.}25+93\mathrm{.}75+81\mathrm{.}5)/7$

$=69\mathrm{.}71($rounded to two decimal places$).$

Finally, we calculate the seasonal index for each day of the week by dividing the average for that day by the overall average:

Sunday: $39\mathrm{.}25/69\mathrm{.}71=0\mathrm{.}56($rounded to two decimal places$)$

Monday: $54\mathrm{.}75/69\mathrm{.}71=0\mathrm{.}79($rounded to two decimal places$)$

Tuesday: $62\mathrm{.}5/69\mathrm{.}71=0\mathrm{.}90($rounded to two decimal places$)$

Wednesday: $74/69\mathrm{.}71=1\mathrm{.}06($rounded to two decimal places$)$

Thursday: $82\mathrm{.}25/69\mathrm{.}71=1\mathrm{.}18($rounded to two decimal places$)$

Friday: $93\mathrm{.}75/69\mathrm{.}71=1\mathrm{.}35($rounded to two decimal places$)$

Saturday: $81\mathrm{.}5/69\mathrm{.}71=1\mathrm{.}17($rounded to two decimal places$).$

These seasonal indices represent the relative amount of meals served on each day of the week compared to the average. For example, the index for Sunday $(0\mathrm{.}56)$ indicates that the restaurant serves about $56\%$ of the average number of meals on Sundays.